Even official tourist brochures admit that this cathedral is not very rich. Characterized by twin towers flanking its entrance, it represents an architectural wedding of Romanesque and Gothic style. The facade is severe enough to resemble a medieval fortress. At one point, the Saracens reportedly used the site of the present Sé as a mosque. When the city was captured early in the 12th century by Christian crusaders, led by Portugal's first king, Afonso Henríques, the structure was rebuilt. The Sé then became the first church in Lisbon. The earthquakes of 1344 and 1755 damaged the structure.

Beyond the rough exterior are many treasures, including the font where St. Anthony of Padua is said to have been christened in 1195. A notable feature is the 14th-century Gothic chapel of Bartolomeu Joanes. Other items of interest are a crib by Machado de Castro (the 18th-c. Portuguese sculptor responsible for the equestrian statue on Praça do Comércio), the 14th-century sarcophagus of Lopo Fernandes Pacheco, and the original nave and aisles.

A visit to the sacristy and cloister requires a guide. The cloister, built in the 14th century by King Dinis, is of ogival construction, with garlands, a Romanesque wrought-iron grill, and tombs with inscription stones. In the sacristy are marbles, relics, valuable images, and pieces of ecclesiastical treasure from the 15th and 16th centuries. In the morning, the stained-glass reflections on the floor evoke a Monet painting.