The Knights Templar held enormous power in Portugal from the 12th to 16th centuries, and largely bankrolled the Age of Discoveries.
Convento de Cristo is known as a convent, but it was built in 1160 as a headquarters for the Knights Templar, the formidable Catholic military that answered to the Pope.
When sovereigns feared the Pope had too much power, the Knights Templar were burned at the stake in France. Portugal however, King Denis I took pity, and instead renamed the knights the Order of Christ.
This new order would answer to the King, but was later demilitarized and converted to an entirely religious order. The subsequent heads of the Order added on to the castle in the centuries to follow.
Additions included cloisters, connecting corridors, an aqueduct, and an expanded chapel, not to mention decadent ironworks, paintings, and tapestries. All of these were built in the various prevailing styles of the day, from Romanesque to Gothic to Renaissance.
Today, the Convento de Cristo is preserved as a museum and has been a World Heritage site since 1983.