Museo Nacional de Arqueología Subacuática

Spain's National Museum of Underwater Archaeology (ARQVA) in Cartagena is one of a kind — the only museum in the country dedicated entirely to underwater heritage, showcasing shipwrecks, ancient amphorae, and artifacts pulled from the Mediterranean seafloor. Entry is just €3, but swing by on a Saturday or Sunday after 2pm and it's free, with guided tours available at 7pm. It's the kind of place that makes the sea feel ancient in the best possible way.