Arecibo Observatory

Arecibo Observatory is the NSF-stewarded historic district in Puerto Rico whose 305-metre radio telescope collapsed on 1 December 2020 and is no longer operational or planned for rebuild. The site’s legacy and preserved dish remnants are now interpreted through the Arecibo C3 STEM Center, which offers exhibits, public programmes and STEM education rather than an active radio-telescope visit. C3’s 2026 pilot reopening provides calendar-controlled access to the Science and Visitor Center, Signals exhibition preview, historic interpretation, scheduled talks and STEM activities; the current ticket page says general public hours are paused in August while the fall calendar is prepared. Tickets must be reserved online at least 24 hours in advance, capacity is limited, and food and vending are unavailable for general visits. The site remains a radio-quiet zone: phones must be in airplane mode and Bluetooth and other wireless devices disabled. Check the current C3 calendar, ticket and visitor guidance before travel.