Qasebeh Qanat
This ancient structure is the oldest and largest qanat in the world. It’s essentially an ancient water system and when used to sustain life.
Excavated between the 4th and 6th centuries BC, this qanat consists of more than 400 shafts, while the main shaft has a 300-meter depth. It’s hard to imagine how a build like this was possible back then. It simply would not work these days.