## 3 Results
### Hotspot Monitoring: Site-Scale Assessment of Looting in Apamea  
The archaeological site of Apamea is an example of 'heritage hotspot', that is, a site of high priority for heritage stakeholders and for which the risk of being damaged is considered high due to the combination of a high probability of incident occurrence, a high degree of exposure, and/or a high  
Figure 3: View of the Citadel of Aleppo (Syria) from Sentinel-2 images acquired on (**a**) 4 August 2016, (**b**) 11 August 2016, (**c**) 14 August 2016, (**d**) 21 August 2016, (**e**) 3 October 2016, (**f**) 5 October 2017, and from (**g**) very high resolution (VHR) Google Earth image taken on 11 August 2016. Labels and polygons indicate the monuments and buildings close to the area of the wall collapse that happened on 11 August 2016. Copernicus Sentinel-2 images in (**a**–**f**) © 2016–2017 European Space Agency—ESA; Google Earth image in (**g**) © 2018 DigitalGlobe. stock of cultural elements at risk. Since the start of the Syrian civil war in March 2011, Apamea has been affected by extensive and repeated looting of archaeological goods [1; 19]. Satellite optical and SAR imagery have been used to estimate that about 45% of Apamea was looted as of October 2014 with evidence of the intensification of looting and changing spatial patterns across the northern and eastern parts of the site, above the main Decumanus, in 2015 [20]. Table 10 in Appendix A lists the VHR satellite images viewable in Google Earth showing the situation from 2011 to mid-2014. In such circumstance, the current approach of national and international heritage initiatives is to prioritize the site and task VHR satellite acquisitions to revisit the hotspot periodically, so as to be able to check the condition of the local heritage and update the records accordingly. From this perspective, freely accessible and regularly acquired HR datasets can contribute cost-effectively to the systematic monitoring of the heritage hotspot and highlight features and changes of new events or intensifications/repetitions of ongoing processes that have been previously mapped. In our experiment, we screened the cloud-free archive of 57 Sentinel-2 images covering Apamea from 20 August 2015 to 17 December 2017 (Figure 4a,b) and we searched for any textural and/or surface reflectance changes occurring within the site walls. The site-specific research question that we could address with Sentinel-2 was whether new looting had affected the western and southern sectors of the archaeological site that were previously unlooted and, if so, whether this could have been seen at the 10 m resolution. Figure 4: View of the archaeological site of Apamea (Syria) from Sentinel-2 images acquired on (**a**) 28 December 2015 and two years later on (**b**) 17 December 2017 with the locations as follows: (1) Cardo Maximus; (2) main Decumanus; (3) second main Decumanus; (4) Roman theatre; and (5) Agora. Zoomed images of the new looted areas detected with the Sentinel-2 time series analysis, southeast of the Roman theatre on (**c**) 6 April 2016 and (**d**) 11 May 2017; west of the Cardo Maximus and the Agora on (**e**) 6 April 2016 and (**f**) 11 May 2017; and east, along the second main Decumanus on (**g**) 20 August 2015, (**h**) 16 February 2016, (**i**) 6 April 2016, and (**j**) 11 May 2017. Copernicus Sentinel-2 images © 2015–2017 European Space Agency—ESA. From 20 August 2015 until the end of 2015, no evidence of new looting clusters was detected at the spatial scale allowed by Sentinel-2 (Figure 4a). Starting from 16 February 2016, owing to a better contrast in the reflectance of looted areas with respect to the surrounding greening land, new looting is clearly visible in at least three sectors: (i) south-east of the theatre (Figure 4c,d); (ii) west of the Cardo Maximus and the Agora (Figure 4e,f); and (iii) in the eastern portion of the archaeological site, along the second main Decumanus (Figure 4g-j).