ShotHotspot has mapped 15 abandoned places in Nomós Piraiós, Attica, ranked by how often they're photographed, viewed and voted for. The most popular are The warriors of Salamina, Stoa of Attalos and Abandoned Athens Ex!t Primitive. Some are private property or unsafe, so get permission before you visit.
We don't know whether you're allowed to visit any of these places. Many are private property, closed to the public or unsafe: get permission from the owner or the relevant authority, and take safety precautions.