St. Peter's Basilica

You cross no fence to enter the world's smallest country — only a white line in the pavement, and suddenly the square has you. Bernini built his colonnade as two open arms, and four centuries later the trick still works: two hundred eighty-four columns gathering pilgrims, tourists, skeptics and pigeons alike toward the obelisk that Caligula shipped from Egypt and the popes taught to tell time.

The sensible traveller comes at seven, when the basilica belongs to the cleaning crews and the light under Michelangelo's dome falls on almost no one; stands on the porphyry disc where Charlemagne knelt; and climbs the cupola — the elevator forgives 231 steps and the drum's leaning spiral collects the rest — for the one view that explains Rome's geometry. The Pietà waits behind her glass, wearing fewer years than her five centuries.

The Guide's honesty: shoulders and knees covered, always — the code is enforced by men who have heard every argument —; the Museums and the Sistine are a different door fifteen minutes' walk away, with their own queue: book online or donate your morning; Wednesday mornings belong to the audience, and the square closes its arms early. And the yellow post office by the square posts real letters: send this postal from the smallest country on Earth.