Also known as underused areas or sites, these places within the already existing morphological urban area that contain a lot of vacant buildings, sites and/or have a lot of inefficient land use such as big one story supermarkets, with large outdoor parking spaces near the city centre. Intensifying the use of these spaces is an important challenge in achieving compact and sustainable cities. Agricultural land and greenfields within the urban fabric (i.e. community gardens; allotment plots; fields surrounded by urban expansion and still exploited; etc.) are not counted as underused.