Coves de Sant Josep hosts Europe’s longest navigable underground river

The Coves de Sant Josep, located in the Plana Baja region of Castellón, Spain, features Europe’s longest navigable underground river. The subterranean river spans 2,750 meters in length.

Visitors can participate in a 40-minute guided tour covering 1,050 meters. The experience includes an 800-meter boat ride through crystal-clear waters and a 250-meter walk. The site maintains a constant temperature of 20°C, making it accessible year-round.

The caves hold significant historical and cultural value, containing prehistoric paintings and engravings recognized as a UNESCO World Heritage site. Archaeological evidence indicates human occupation dating back to the Upper Paleolithic period, approximately 17,000 years ago, with subsequent use by Iberian and Roman cultures. The site also served as a refuge during the Spanish Civil War.