A natural depression in Puerto Rico's limestone terrain once hosted the world's largest single-dish radio telescope, the Arecibo Observatory. Constructed in 1963, the telescope used a massive 305-meter dish made of 38,778 aluminum panels, supported by steel cables. This design took advantage of the area's unique karst landscape—deep valleys and limestone hills—to create a cost-effective structure. However, the observatory collapsed in December 2020 when a critical steel cable failed, causing a 900-ton platform to fall onto the dish below. Fortunately, the observatory had been closed for several days prior, and no injuries were reported. The Arecibo Observatory was originally built by Cornell University under a contract with the U.S. government’s Advanced Research Projects Agency as part of Cold War-era research. Its location allowed for an innovative design that minimized construction costs. The telescope was the largest of its kind until China's Five-hundred-meter Aperture Spherical Telescope (FAST) was completed in 2016. Despite its size, Arecibo's unique feature was its ability to emit radio waves, allowing it to map the surfaces of celestial objects and detect signals from distant pulsars—rapidly rotating neutron stars that emit regular pulses of radiation. The decline of the telescope began in August 2020, when an auxiliary cable broke, damaging the main reflector and the secondary Gregorian dome. Engineers worked on repair plans, but on November 6, 2020, another main cable failed unexpectedly. Analysis showed that the remaining cables might not have been strong enough to support the structure. After reviewing engineering reports, the National Science Foundation, which owned the observatory, decided to decommission the telescope, declaring it irreparable. The collapse finally occurred on December 1, 2020, when a third cable broke, causing the platform to fall. The loss of Arecibo had immediate consequences for scientific research. Programs like NANOGrav, which had been monitoring pulsars for over a decade to detect gravitational waves, were severely impacted. Despite its collapse, the site remains a point of interest for visitors, though it now stands as a collection of broken cables and metal sheets at the bottom of the karst basin. The observatory was not only a scientific marvel but also a symbol of human ingenuity and our quest to understand the universe.