walls and castle of mértola in aerial view and guadiana river between mountains, alentejo portugal

town village fortification tourism vacation castle wall landmark building coast river walls mértola aerial view guadiana between mountains alentejo portugal authentic trees panoramic banks houses roofs countryside construction fort fortress heritage battlement panorama defense cityscape landscape natural stone stairs baixo courtyard attraction scenic old summer historic hill tower monument famous touristic travel architecture valley viewpoint beja mertola portuguese europe