St. Peter's Basilica

St. Peter's Basilica is the largest church in the world and arguably the single most important building in Christianity, built over the site where the apostle Peter is believed to be buried. The current building, which took 120 years to complete (1506-1626), represents the combined genius of Bramante, Raphael, Michelangelo, Maderno, and Bernini. Michelangelo designed the dome (completed after his death), and it remains one of the most recognizable silhouettes in architecture. Inside, the scale is almost disorienting — the nave is 186 metres long, and the dome rises 136 metres above the floor. Bernini's baldachin (the bronze canopy over the papal altar) stands 29 metres tall and somehow doesn't overwhelm the space. Michelangelo's Pietà, carved when he was just 24, sits in the first chapel on the right and is one of the most emotionally powerful sculptures ever made. The Vatican Grottoes below contain papal tombs, and climbing to the top of the dome rewards you with an extraordinary panorama over Rome and a vertigo-inducing look straight down into the interior. Despite being free to enter, this is not a casual visit. Security lines can stretch to an hour in peak season (get there early, before 08:00 if possible). The dress code is enforced — no bare shoulders or knees. And be aware that it's an active place of worship; Mass is celebrated daily and parts of the basilica may be cordoned off during services.