## 2 Method  
In this study, we selected eleven different industrial heritage sites, including both isolated constructions and large building complexes, located in the autonomous regions of Andalusia, Castile-La Mancha, Murcia Region, Basque Country, Castile-Leon, Catalonia, and Asturias. They represent some of the most heavily industrialized sites in Spain's history, which is why it matters so much to ascertain the current level of digital transformation of their management and promotion. In some cases, they are areas with a long-standing mining tradition and a strong initial environmental impact, with interesting constructions and tools of different types [25]. Spectacular landscapes that still bear the deep traces of an activity that lasted a very long time and has resulted in intensive regeneration [26]: Riotinto (Huelva), Almaden (Ciudad Real), La Union (Murcia), and Samu\(\mathrm{\SIUnito}\) (Asturias). The Anana Salt Mines (Alava) are the last example of mining sites selected in the research project. All other cases involve specific buildings and constructions from different productive sectors adapted to manufacturing techniques. Some date back to the pre-industrial era, like the San Blas Ironworks (Leon), the Royal Glass Factory in La Granja de San Ildefonso (Segovia), and the Royal Spanish Mint in the city of Segovia [27,28]. Others date back to the industrial era per se, such as the La Encartada Beret Factory in Balmaseda (Vizcaya), the water lift in Cornella del Llobregat (Barcelona), and the Vapor Aymerich, Amat y Jover textile factory in Tarrasa (Barcelona) (Figure 1). Figure 1: Location of buildings and areas analyzed: 1. Riotinto mining area; 2.Almaden mining area; 3. La Union mining area; 4. Samu\(\mathrm{\SIUnito}\) mining area; 5. San Blas Ironworks; 6. Anana Salt Mines; 7. Royal Glass Factory; 8. Royal Spanish Mint; 9. La Encartada Beret Factory; 10. Water lift; 11. Vapor Aymerich, Amat y Jover textile factory. Source: [PERSON] (UNED SIG Laboratory). From a methodological viewpoint, an extensive review of the scientific literature has been conducted to verify the different theoretical approaches present in the smart tourism field, the application of new digital technologies, and the proposed innovative resource management models. Also with regard to the method, one proposal put forward is to analyze them by using different variables present on their webpages, creating an index and conducting a survey. Use of the web popularity index (WPI) is proposed to check and measure the variables regarding the content and information available on the webpages. The WPI, which ranges from 0 to 1, measures the percentage compliance of a broad range of selected variables that each industrial heritage site had in February 2019. The results are analyzed both in terms of constructions and sites and of variables; in other words, identifying the mean value obtained in each building and site for all variables and of each variable for all case studies. The WPI is a very interesting tool in this investigation. It is considered a fundamental part of the study not previously used by other researchers. Obtaining the indicator is quick and simple, and the results are very direct and understandable from the point of view of the technological reality used in the case studies. The WPI quantifies different and highly significant qualitative aspects and is very useful in two ways: first of all, it is an efficient, straightforward, and simple way of approximating the information facilitated to visitors; and, secondly, it can be used to categorize the sites and buildings selected in terms of their level of application and display in digital environments. A key part of the method has been the survey, carried out between the months of March and April 2019, among the technical managers and directors of the selected industrial heritage sites. The blocks and questions are listed in Table 1 below, and the levels of response were limited to three categories: agree, disagree, and no opinion.