## 3 Results
### Dynamic Detection of Changing Features: Urban Development around the WHS of Cyrene
In 2014, the spatial trend changed and urban development happened across the whole rural landscape (yellow polygons in Figure 6a), to a point of reaching the southern boundary of the Cyrene archaeological site (Figure 6c). In particular, works for new roads and blocks were ongoing in June 2014 and, after only one year, a new settlement was already developed very close to the ruins of the Sanctuary of Demeter and Kore (Figure 6c; see also References [5; 22]). In the years covered by the Sentinel-2 time series (2016-2017), new block features were mostly concentrated in the landscape of the south necroolis (Figure 6b), thus, highlighting the increasing impact on this area up to present days (Figure 6d). The two examples reported in Figures 5 and 6c prove that these urban feature patterns have a short life cycle. On average, from the first appearance to the full development, a cycle lasts one year in total, with the construction phases mostly happening during a few months. In this regard, the high temporal frequency provided by Sentinel-2 is extremely valuable to achieve high temporal granularity to capture new incidents of urban development. It is worth acknowledging that, because of their size, the block features are equally well detected in both Sentinel-2 and Google Earth images, thus, resulting in no omissions of block feature mapping with HR and VHR data due to the different spatial resolution. Figure 5: The life cycle of the typical block feature of new urban development in the cultural landscape surrounding the Cyrene WHS (Libya), as reconstructed based on the VHR Google Earth satellite imagery: (**a**) the topsoil is initially excavated (24 June 2015); (**b**) the road pavement is laid down (13 July 2015); (**c**) the road grid enclosing land lots is completed (4 August 2015); (**d**,**e**) the land lots are being populated by houses, dwellings, and farming activities (12 February 2016 and 5 July 2016). Google Earth imagery © 2018 DigitalGlobe. Figure 6: The spatial and temporal distribution of block features of new urban development across the cultural landscape of the Cyrene world heritage site (WHS) and in the surroundings of the modern town of Shahat (Libya), as mapped through (**a**) Google Earth (2009–2015) and (**b**) Sentinel-2 time series (2016–2017). Note that no block features were detected prior to 2012. Zoomed views of the urban development (**c**) close to the Sanctuary of Demeter and Kore and (**d**) west of Shahat, in the landscape of the south necroolis. Blocks in (**a**,**c**) are overlapped onto Google Earth imagery acquired on 25 December 2006, while blocks in (**b**,**d**) are overlapped onto Copernicus Sentinel-2 image acquired on 4 October 2015. © 2015 European Space Agency—ESA). Google Earth imagery © 2018 DigitalGlobe. Of course, the level of detail achieved with Sentinel-2 for feature delineation is much lower than with VHR satellite images. However, even at very local scale, that is, focusing on hotspot areas to search for changes, the spatial resolution of Sentinel-2 can already be enough and the VHR imagery may not be necessary, at least to undertake the first assessment. An example is found in the hotspot identified near the Sanctuary of Demeter and Kore (see Figure 6c). In March 2014, when Sentinel-2 images were not yet available, DigitalGlobe imagery showed no evidence of building construction in close proximity to the archaeological ruins (Figure 7a). Three months later, the first roads and dwellings were built (Figure 7b); after one year, the new block feature had already achieved a mature stage of development, with evidence of further excavation along the road facing the ruins (see blue polygon in Figure 7c). By coincidence, this situation was captured in a DigitalGlobe image that was acquired on 24 June 2015, that is, when the Sentinel-2A satellite was launched. The first cloud-free Sentinel-2 image taken on 4 October 2015 depicts the same situation (Figure 8a).