Caves of Poço Velho

The Caves of Poco Velho are two natural caves with interconnected galleries in central Cascais, Lisbon district. Formed 1.6 million years ago by water seeping into limestone, they were primarily used as a necropolis during the Final Neolithic and Chalcolithic periods (4th-3rd millennia BC), with approximately 115 burials identified. First excavated in 1879 by Carlos Ribeiro and again in the 1940s, artifacts include a notable Neolithic necklace of green minerals, slate, limestone, and shells dating to c. 4000 BC. Finds are displayed at the Cascais Town Museum and the National Geological Museum.