The Arecibo Observatory was the world's largest single-dish radio telescope for over fifty years, its 305-metre reflector nestled into a natural sinkhole in the karst hills south of Arecibo. It featured in the films GoldenEye and Contact, detected the first binary pulsar, and was central to the Search for Extraterrestrial Intelligence project. The dish collapsed in December 2020 after cable failures, and the main telescope is no longer operational.
The visitor centre and Angel Ramos Foundation Science and Visitor Center museum remain open, with exhibits on radio astronomy, atmospheric science, the history of the facility, and what the future of the site might look like. The site still contains other scientific instruments, and plans for the observatory's future are ongoing. It remains one of Puerto Rico's most visited attractions despite the collapse — the scale of the former dish is still visible in the sinkhole, and the story of its work and fall is genuinely compelling.