Igreja de São Roque

From the outside, the Igreja de São Roque looks like nothing — a plain, beige facade that most visitors walk past without a second glance. This is one of the greatest architectural bait-and-switches in Europe. Step inside and your jaw drops: the ceiling is a trompe l'oeil masterpiece that appears to be a three-dimensional barrel vault but is actually a flat painted surface. It was created by Francisco Venegas in the late 16th century and is one of the earliest examples of this technique on the Iberian Peninsula. The church was the first Jesuit church in the Portuguese world, established in 1553, and the Jesuits clearly believed in surprise as a conversion tool.

But the real showstopper is the Chapel of St. John the Baptist, the fourth chapel on the left. King João V commissioned it from Italian architects Luigi Vanvitelli and Nicola Salvi (yes, the man who designed the Trevi Fountain) in the 1740s. The chapel was built entirely in Rome, blessed by the Pope, then dismantled, shipped to Lisbon in three ships, and reassembled here. It is encrusted with lapis lazuli, amethyst, alabaster, Carrara marble, gold, silver, and ivory. At the time of its construction, it was reportedly the most expensive chapel in the world — a title it may still hold. The mosaic panels, which look like oil paintings, are actually made of tiny stones assembled in Rome with a precision that borders on obsessive.

The adjacent museum houses one of the finest collections of Italian Baroque sacred art outside Italy, along with vestments embroidered with gold thread so fine they look like paintings on fabric. The whole experience — the deceptive exterior, the theatrical interior, the insane opulence of one chapel — encapsulates something essential about Portugal: a small country that punched far above its weight and spent the proceeds with spectacular excess.