Embedded into the top of a hill, Villa Ypsilon in the Greek seaside village of Messenia has a Y-shaped green roof promenade that is an extension of the terrain.  Photo 6 of 14 in 13 Subterranean Homes That Are Out of This World

13 Subterranean Homes That Are Out of This World

6 of 14

Embedded into the top of a hill, Villa Ypsilon in the Greek seaside village of Messenia has a Y-shaped, earth-covered roof promenade that looks as if it's an extension of the terrain.