Giolitti

Rome's most famous gelateria, scooping since 1900, two minutes from the Pantheon. Popes, presidents, and every tour group in the city have stood in this line — the pistachio and hazelnut hold up to the reputation.

Order and pay at the register first, then take your receipt to the counter — the standard system at most historic Roman gelaterie, and one that trips up first-time visitors who queue at the wrong spot. Being two minutes from the Pantheon means it's busy essentially all day; a stop early morning or late evening avoids the worst of it.