The quadrangular Tower of Belém is a monument to Portugal's Age of Discovery. Erected between 1515 and 1520, the Manueline-style tower is Portugal's classic landmark and often serves as a symbol of the country. A monument to Portugal's great military and naval past, the tower stands on or near the spot where the caravels once set out across the sea.

Its architect, Francisco de Arruda, blended Gothic and Moorish elements, using such architectural details as twisting ropes carved of stone. The coat of arms of Manuel I rests above the loggia, and balconies grace three sides of the monument. Along the balustrade of the loggias, stone crosses represent the Portuguese crusaders.

The richness of the facade fades once you cross the drawbridge and enter the Renaissance-style doorway. Gothic severity reigns. A few antiques can be seen, including a 16th-century throne graced with finials and an inset paneled with pierced Gothic tracery. If you scale the steps leading to the ramparts, you'll be rewarded with a panorama of boats along the Tagus and pastel-washed, tile-roofed old villas in the hills beyond.

Facing the Tower of Belém is a monument commemorating the first Portuguese to cross the Atlantic by airplane (not nonstop). The date was March 30, 1922, and the flight took pilot Gago Coutinho and navigator Sacadura Cabral from Lisbon to Rio de Janeiro.

At the center of Praça do Império at Belém is the Fonte Luminosa (the Luminous Fountain). The patterns of the water jets, estimated at more than 70 original designs, make an evening show lasting nearly an hour.