The Jeronimos Monastery is the most impressive symbol of Portugal's power and wealth during the Age of Discovery. King Manuel I built it in 1502 on the site of a hermitage founded by Prince Henry the Navigator, where Vasco da Gama and his crew spent their last night in Portugal in prayer before leaving for India. It was built to commemorate Vasco Da Gama's voyage and to give thanks to the Virgin Mary for its success.
Vasco da Gama's tomb was placed inside by the entrance, as was the tomb of poet Luis de Camões, author of the epic The Lusiads in which he glorifies the triumphs of Da Gama and his compatriots. Other great figures in Portuguese history are also entombed here, like King Manuel and King Sebastião, and poets Fernando Pessoa and Alexandre Herculano.
The monastery was populated by monks of the Order of Saint Jerome (Hieronymites), whose spiritual job was to give guidance to sailors and pray for the king's soul. It's one of the great triumphs of European Gothic (UNESCO has classified it a World Heritage monument), with much of the design characterized by elaborate sculptural details and maritime motifs. This style of architecture became known as "Manueline," a style that served to glorify the great "discoveries" of the age.