## 5 Conclusions  
In this paper, we prove that, at the right spatial scale and for features that are a few meters in size, Sentinel-2 can be successfully applied for the condition assessment of heritage sites. The results of our research suggest that the general idea that 'high resolution' Earth observation sensors are of limited use compared to sensors operating at'very high resolution' should be reconsidered. We tested Sentinel-2 on both single localised events (for example, wall collapses) and sequences of recurrent incidents (for example, illegal excavations of archaeological sites), also searching for features of different size, spanning from clusters of meter-scale features (for example, looting holes) to single medium-size urban features (for example, road and building blocks, with dimensions of a few tens of meters). Despite the obvious constraint in the spatial resolution that we acknowledge in the discussion of the results (see Sections 3 and 4), Sentinel-2 allowed for the detection of events of potential relevance for heritage conservation in all the demonstration sites investigated in this paper. In renowned hotspots, the availability of prior knowledge of the processes to expect and of the baseline condition of the local heritage increases the likelihood for Sentinel-2 to capture textural anomalies or changes of surface reflectance properties that could relate to site disturbances or incidents of potential damage. In this regard, the case studies of Aleppo and Apamea (Syria) provide a clear demonstration. However, to investigate processes such as urban development that manifest through spatial and temporal patterns of distinctive features, approaches of feature extraction making the best use of the two properties that make Sentinel-2 quite advantageous compared to VHR satellite imagery--the very short revising time between two consecutive acquisitions and the large swath width--are promising. These conditions cannot always be achieved using VHR data, as acknowledged in the literature ([PERSON], 2015). Sentinel-2 could contribute to addressing this limitation in the framework of a multi-scale condition assessment of heritage sites. For instance, a multi-temporal HR satellite-based condition assessment could provide information to schedule a targeted survey with ad hoc VHR imagery. The test that we ran on the block features associated with urban sprawl in Cyrenaica (Libya) suggests that Sentinel-2 can well become an extremely useful source of information to screen wider regions and undertake comparative analyses of the condition of different heritage sites. The approach that we demonstrate in this paper with Sentinel-2 may be applied to other satellite missions, such as Landsat-8. However, it is worth mentioning that the spatial resolution of Landsat-8 is coarser than that of Sentinel-2 (15 m for the panchromatic band and 30 m for the visible to short-wave infrared channels), the revisiting time longer (16 days) and the swath smaller (185 km). Therefore, Sentinel-2 appears to be a good candidate among the current freely accessible space solutions to bridge the gap between HR and VHR optical imagery for the condition assessment of heritage sites. We can easily anticipate that the implementation of automatic processing chains searching for and extracting features through long time series would be a technological development accelerator towards the systematic use of Sentinel-2 for the condition assessment and monitoring of local to wide areas of study. This automation should provide a complement to the analyst-driven methodsthat currently represent the state-of-the-art methods in this field [6] and, ideally, help to mitigate the drawbacks of manual examination. The latter is still a common practice across the archaeological and heritage community. However, although this approach has been proved to lead to reliable and successful mapping results, the community has started to question it from a methodological point of view.