The openness of a destination to international markets is considered a key strategy for generating income from abroad, attracting foreign direct investments, boosting its brand image globally, and strengthening its regional competitiveness and economic growth [1]. Under this prism, intensive and, simultaneously, low-cost marketing efforts have become a challenging task for making a destination attractive globally [2]. The role of sustainability in this context is considered vital, as it can be considered a part of a destination’s overall image ^[3][4][3,4]. Travelers themselves contribute to promoting and keeping a destination sustainable with their behavior and their story posts on social media [5].

Nowadays, social media platforms have an important role in destination marketing strategies, providing travelers with the opportunity to share their travel experiences in real time [6]. Regarding tourism destinations, Instagram offers a wide range of benefits, especially when financial and marketing resources are limited [7]. As of January 2022, Instagram is the third (after Facebook and YouTube) among the top leading social networking sites worldwide with 1478 million active users and the first selected media platform for marketing planned campaigns (the advertising expenditure in Instagram is 60% higher than the other social media platforms) [8].

Moreover, Instagram is well known as the first social media platform that offered the possibility of social interactions with other users acting as real-life friends [9]. This parasocial engagement, i.e., the engagement occurred through digital interaction between a viewer and a character that creates a virtual/imagined and trustful relationship [9], has led Instagram to become one of the most popular platforms in contemporary influencer marketing literature [10]. As a result, Instagram users with high engagement levels have been first perceived as peers by their followers, presenting significant persuasive/influence power [11].

Influencer marketing has seen the most noteworthy growth on Instagram due to its wealth of visual affordances and shopping/selecting features [11]. In fact, Instagram has been ranked as the favorite platform of marketers for influencer marketing [12]. According to Statista’s findings for 2022 [13], Instagram alone accounts for over 500,000 active influencers with more than 15,000 followers, which constitutes 39% of all Instagram accounts. Among this group of active influencers, 81% are followed by anywhere between 15,000 and 100,000 people [13].

The enormous use of Instagram combined with the lifestyle of influencers (by sharing their traveling moments and memories online) has boosted influencer marketing [6]. Expenditure on influencer marketing has escalated from USD 1.7 billion in 2016 to USD 16.4 billion in 2022 [14]. Moreover, 84% of marketers characterize influencer marketing as one of the most effective tools in current marketing and branding strategies globally [15]. As a result, influencer marketing can be perceived as a very effective destination marketing tool not only for cities, places, or countries but also for National Tourism Organizations (NTOs), Destination Management Organizations (DMOs), travel agencies, venues, or hotels [16]. In contemporary tourism literature, digital influencers consist of key destination spokespersons who stimulate tourists’ preferences and boost the image of a destination [4]. However, there seem to be no studies—at least according to authe researchersors’ knowledge—that examine the impact of travel influencers in sustainable destinations. This would be interesting as these destinations offer many advantages of economic and social development with a low environmental burden and are constantly multiplying and present a growing interest [17].

In addition, the clear motives of users for the selection of sustainable destinations still seem to remain vague [7]. With the growing popularity of Instagram and the significance of influencer marketing in sustainable tourism, additional information and methods of data gathering that have not yet been examined in depth could support the marketing strategies of a destination [16]. Existing studies almost exclusively use traditional methods, such as questionnaires, for these purposes [18]. However, geo-location social media data, in particular, seem to be among the upcoming data collection trends for studying the travel demand of a destination [19], seeing as they represent check-ins at the venue, shared content, and/or hashtags that are connected to users’, travelers’, and travel influencers’ geo-locations [20]. Moreover, these data have been considered beneficial elements for further boosting a destination’s brand image, which is usually represented by geographic elements, such as coastal, mountainous, rural, and urban areas [21]. However, no evidence from sustainable destinations exists, although these elements could be part of the overall sustainability factor that is essential for a destination’s internationalization in an increasingly competitive tourism market, usually measured at a national level [17].

2. Internationalization of Destinations and Inbound Tourism

In tourism, internationalization is often associated with product and destination competitiveness ^[22][23] and is considered a trigger factor for the formation of a destination’s image and growth ^[23][24]. Territorial resources that support a region’s economic dynamics, connections, and networks which allow tourists to reach the destination and facilitate their movements within it, as well as companies that transform a region’s endogenous resources into tourist products, appear to be crucial elements that contribute to the internationalization of a destination ^[24][25]. Moreover, internationalization is aligned with the concept of territorial economic development that values quality, innovation, identity, and differentiation by focusing on the attractiveness of inbound tourism rather than domestic ^[25][26]. Inbound tourism, i.e., tourism coming from abroad into a country, represents a significant revenue source on a country level and constitutes an important activity in the exportation category, creating a high source of business activity, income, employment, and foreign exchange for the local markets ^[22][25][23,26]. The significance of international inbound (“foreign”) tourism has been fully highlighted for its economic importance in tourism destination areas ^[23][24]. By eliminating the barrier of distance, inbound tourism benefits the destination, as it brings many benefits and resources into a developing or less developed country ^[24][25]. As a result, Buhalis ^[26][27] states that inbound tourism is highly linked with the internationalization of destinations, where the mobility of tourists creates links beyond borders. In the same research, a key conclusion refers to the tourism–growth relationship ^[26][27], concluding that less developed countries are more likely to benefit from international/inbound tourism ^[26][27][27,28].

3. Sustainability and Tourism Destinations

A destination’s internationalization is important as it creates opportunities for foreign income flows to the destination’s economy, as well as information and knowledge sharing, improvements of the destination’s reputation, low dependency on domestic tourism sources, and high levels of overall sustainability ^[28][29]. Glyptou et al. [17] proceed to a cluster analysis of performance rankings of Mediterranean destinations, concluding that sustainable destinations are characterized by high economic and social performance combined with a low environmental footprint. However, maintaining and enhancing a sustainable destination’s image in international markets is a challenging task ^[29][30]. Romao et al. ^[30][31] build their research based on structural analysis regarding the motivation and satisfaction of global tourists from different nations and cultures, stating that there is an opportunity to attract long-haul visitors who spend more and behave sustainably to destinations; this is even more important when domestic tourists cannot support the development of a destination ^[31][32]. A sustainable tourism destination considers assuring the ecological or environmental impact ^[32][33]. This means that, among other things, it should take care of the environmental resources for achieving high levels of positive impact on society, nature, and visitors, and, simultaneously, maintain the cultural sustainability of the destination and its overall brand image awareness ^[33][34][34,35]. A high percentage of destinations still present limited brand awareness in terms of quality among potential tourists ^[35][36] who use the internet as their key source of information ^[36][37]. Social media platforms can contribute to a traveler’s awareness process of different destinations ^[37][38]. Through their rapid level of penetration, low-cost results, and global reach, these platforms comprise one of the main tools of a destination marketing strategy ^[38][39]. Therefore, the relationship between social media and destination marketing is highly interrelated ^[39][40]. Contemporary destinations seek increased brand awareness through users’/travelers’ social media engagement ^[40][41].

4. Social Media, Parasocial Interaction, and Influence

According to the literature, direct communicating, engaging, and sharing are the main three characteristics of social media that contribute to shaping travelers’ perceptions on a destination’s image formation ^[41][42][42,43]. With shared experiences on social media constantly increasing, consultation before and during the trip, as well as consideration of content generated by other travelers (as influencers) gaining high importance ^[43][44], engagement through digital platforms and social media influencers has become a significant component of the internationalization of tourism destinations ^[44][45]. Social media has transformed users from being passive recipients of marketing messages to being communicators who can openly share their opinions regarding products, services, or destinations ^[45][46][46,47]. Being this type of communicator has created the term “influencer”. Several researchers stress the role and importance of these influencers in social media communication. For example, Menge ^[47][48] points out that they are characterized by the key elements of the general theory of power, namely (1) the ability to use force digitally, (2) the accessibility to digital resources, and (3) the collective acceptance from several groups of social media users globally. Vrontis et al. ^[48][49] highlight the emerging trend of social media content creators, known as social media influencers (SMIs), and the power generated by them as a main source of information for their audience. Nowadays, influencers play an important role in international social media marketing strategies ^[49][22]. Shan et al. [50] emphasize the endorser/promoter’s impact on influencer marketing, underlining the role of parasocial interaction in the influencer and users’ relationship. In more detail, Kim’s study [15] tries to analyze the theory of parasocial interaction by examining users’ illusionary and interactive relationships with media personas under the scope of viewership’s influence, concluding that users tend to present higher interaction with their media personas when they are closer to their everyday life. Lee et al. [51] conclude that the role of parasocial interaction in influencer marketing is significant in the followers’ active engagement and the creation of strong relationships with influencers, who are perceived as relatable and intimate figures in recommending products or destinations.

5. Instagram and Influencers

Instagram has proven to be the most popular social media platform presenting a high level of engagement in terms of content shared, while it also exists as the most preferable resource for inspiration and information [1]. Instagram was chosen by Breves [9] due to its large advertising revenue and its effectiveness as a platform for testing the relationship between followers and social media influencers during advertising campaigns. Social-media-based interaction has created a vital shift in connectivity between products, services, and users. As users love visual content, Tariq examines user-generated content on Instagram under two major types of information [52]: (a) geographic and temporal information, and (b) the visual content of the photo or video that provides valuable sources for generating insights, where he concludes that geographic information has a key role of post promotion. Backaler [53] describes that Instagram travel influencers could even be characterized as representatives of destinations, in the sense that they shape travelers’ decisions to choose a destination while presenting a place [53]. By proceeding to a cross-factor analysis, he concludes that the number of followers, the behavior towards the influencer’s audience, and the engagement under posts comprise key factors in evaluating the power of travel influencers for shaping audience attitudes [53]. If they present a high level of influence, they create a win–win strategy for tourism brands as virtual brand ambassadors in the era of destination marketing [54]. Ingrassia et al. [55] use netnographic analysis combined with the AGIL model approach (Adaption, Goal attainment, Integration, and Latent pattern maintenance) to measure the power of Chiara Ferragni’s—one of the most famous Instagram influencers—activity and communication via her Instagram profile on promoting Italian tourist destinations worldwide to her loyal followers. The loyalty of users is also crucial [56], and many individuals tend to become increasingly interested in the tourist community by reading personal travel evaluations and following Instagram influencers who promote sustainable tourism [6]. This indirect influence seems to accelerate the decision-making process by the followers, as it creates the willingness to choose the same destination [57].

6. Instagram Travel Influencers and Location-Based Social Media Data

The rise of influencer marketing as a cost-effective and high expansion results tactic of marketing has created new types of influencers in the tourism sector, such as Instagram travel influencers [58]. The selection of destinations can be differently associated with the group of tourists due to the different preferences of people influenced by their country of origin [59]. There have been many attempts to analyze travel behavior and location selection in a way that takes into consideration tourists’ preferences, as well as their influences from travel opinion leaders through social networking sites [60]. Vu et al. [61], introduce new data sources derived from user-generated content —called location-based social media data—tested under the spectrum of influential and destination marketing. These sources are derived by location-based social networks (LBSNs), where the connections and interactions between users are based on creating virtual data that are connected to a specific location ^[7][20][7,20]. Li [59] moves a step forward and tries to examine the contribution of geo-location data, as presented by celebrity influencers’ posts, on the multi-day and multi-stay travel planning of users. The above two studies conclude that location-based social media data, when presented by influencers, are key drivers for the users’ selection of a destination ^[59][61][59,61]. With the advancement of the Global Positioning System (GPS) technology, geographical information can be stored in so-called geo-tagged photos [7]. The geographic and temporal information make influencer-generated posts an interesting source for the study of tourism destinations and the tourists’ decision-making process [54]. Chen et al. [62] study location-based social networking platforms with the use of GPS and new marketing tools (usually referred to as check-in or geo-tag recommendations), concluding that these tools provide people with the ability to share their locations among their social communities when they decide to share their geo-location information. Vassakis et al. [63] examine the tourism recommendation system using geo-tagged photos and social platforms’ Application Programming Interface (API) without considering the role of the influencer’s parasocial ability during the posting process, presenting a partial point of view regarding the influence of geo-location data on users’ engagement. Besides static posts containing normal text, hashtag(s), and/or check-in data, referring to the location of Instagram stories is a common practice used in the promotion of tourism destinations by travel influencers [20]. An Instagram influencer’s location history consists of (a) the rating history (e.g., per visited location) and (b) the check-in history followed by the related check-in location/geo-tag and geo-location hashtag [64]. When it comes to geo-tags/hashtags, the English language is generally used by Instagram travel influencers for boosting visibility and approaching more multilingual users ^[18][65][18,65].