Although a Google search doesn't show many image results, parapet is the right word for the place where the guy is lying.
parapet - [ˈper-ə-pət , -ˌpet, ˈpa-rə-] A low wall along the edge of something high such as a bridge or roof, a low wall or railing along the edge of a balcony, roof, etc.
Etymology - 1580s, from Middle French parapet "breastwork" (16c.), or directly from Italian parapetto, from para- "defense" (see para- (2)) + petto "breast," from Latin pectus (see pectoral (adj.))
The above picture shows how the Italian word "parapetto", which means "supports the chest", fits perfectly what the structure is supposed to be used for.