Castelo do Queijo also known as Forte de São Francisco Xavier, is a castle/fort in Porto

Porto

Porto , also known as Oporto in English, is the second largest city in Portugal and one of the major urban areas in the Iberian Peninsula. Its administrative limits include a population of 237,559 inhabitants distributed within 15 civil parishes...

, Portugal

Portugal

Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

. This fort is placed in the sea side near and the wall facing the sea is often hit by the waves depending on the tides. The fort was given the name of Castelo do Queijo because it is built in the top of a rock that resembles a "piece of cheese."