You may be surprised to discover that the cathedral of Rome is not St. Peter's but this church. (St. Peter's is in Vatican City, technically not a part of Rome.) Dominating the piazza whose name it shares, this immense building is where the pope officiates in his capacity as bishop of Rome. The towering facade and Borromini's cool baroque interior emphasize the majesty of its proportions. The cloister is one of the city's finest, with beautifully carved columns surrounding a peaceful garden.

The adjoining Palazzo Laterano (Lateran Palace) was the official papal residence until the 13th century, and is still technically part of the Vatican. It houses the offices of the Rome Diocese and the rather bland Museo Storico Laterano (Lateran Historical Museum). Behind the palace are the 4th-century octagonal Battistero di San Giovanni (St. John's Baptistery), forerunner of many similar buildings throughout Italy, and Rome's oldest and tallest obelisk, brought from Thebes and dating from the 15th century BC. COST: Cloister EUR2.50, museum EUR3.50.