Belen Tower Fortification Fortified structure on an island in the Tagus River in the eponymous area of Lisbon. It was built in 1515-1521 by Francisco de Arruda in honor of Vasco da Gama's discovery of the sea route to India and served alternately as a small defensive fortress, gunpowder store, prison, and customs. https://opensea.io/assets/matic/0x2953399124f0cbb46d2cbacd8a89cf0599974963/96203920715680885258366468665050395044696175479545047973777732732946583912460/