Where is the Arecibo Observatory located?

The Arecibo Observatory was located in Puerto Rico, near the city of Arecibo, in a karst depression. For decades it was famous for its 305-m radio dish and its work in radar astronomy, pulsar studies, and atmospheric science. The observatory suffered a major collapse in 2020 and was subsequently decommissioned. Before that, it played a major role in planetary radar and the search for extraterrestrial intelligence.