Torca del Carlista (English: Carlista Cavern) is a large limestone cavern found in Cantabria, Spain, approximately from the city of Bilbao. The entrance, up the slopes of the Cantabrian Mountains, is only a single metre (3 feet) wide. The entry passage descends some vertically in a narrow chimney before opening up into the cavern's main gallery. Some long and wide, the total surface area of the cavern exceeds 20 acres, or . The main chamber is the fifth-largest underground chamber in the world, with a ceiling that reaches at its highest point.