Castle of Amposta Monument · Amposta, Montsià, Tarragona The Castell d'Amposta, which gives its name to the capital of the Montsià, was the seat of the Hospitaller castellany of Amposta from when, around 1150, Ramon Berenguer IV ceded the territory to the Order of the Hospital of Saint John of Jerusalem, which established its commandery there. In 1280 King Peter the Great exchanged it for other territories, and in 1384 it passed to the Order of Sant Jordi d'Alfama. Between 1465 and 1466 it withstood a siege during the Catalan civil war, until it surrendered on 21 June 1466. Today Gothic remains survive: an ogival arch more than 6 metres high, storage chambers from the 14th-15th centuries, the foundations of the Torre de Sant Joan, stretches of the wall beside the river, and a double moat cut into the rock, about 6 metres deep. It is declared a cultural asset of national interest. Photo: Enric (CC BY-SA 4.0) What to see and do in Amposta