Syntagma — "Constitution" — is the formal heart of Athens, the square where the city gathers to celebrate, protest, and change trains. On its east side the neoclassical Old Royal Palace houses the Greek Parliament, and in front of it the Tomb of the Unknown Soldier is watched around the clock by the Evzones, the kilted presidential guard whose stiff-legged Changing of the Guard happens on the hour; the full ceremony, with the marching band, comes on Sunday at 11am.
The square is the hinge of the centre. The pedestrianised Ermou shopping street runs west from here toward Monastiraki, the grand old Hotel Grande Bretagne anchors the northern corner, and the metro station beneath the square doubles as a small museum, with the layers of excavated city left exposed behind glass. South and east the monumental quarter opens up — the green sweep of the National Garden, the Zappeion exhibition hall, the toppled columns of the Temple of Olympian Zeus, and the white-marble horseshoe of the Panathenaic Stadium are all within an easy walk.
It is more a place you move through than linger in, but almost every Athens visit passes through Syntagma sooner or later. Time your arrival for a changing of the guard, then slip into the gardens behind to escape the traffic.