Athens has three hills the tourists climb and one they don't: the Lofos Nymfon, the Hill of the Nymphs, rising quietly above Thiseio with an observatory on top instead of a temple. This is the evening walk — short, green, and ending with the Acropolis seen side-on from ground almost nobody else stands on.
Start at Thiseio on the great pedestrian promenade, the Acropolis on your left, and walk to the foot of the hill. The domed church of Agia Marina sits over a far older rock-cut shrine; climb past it into the stepped lanes, where houses stand straight on the bare limestone.
The summit holds the National Observatory, the Asteroskopeio, Greece's oldest research institution, built in 1842 in cool Doric marble by Theophil Hansen. From the open ground beside it the Acropolis stands across the valley and the whole city falls away below — best at dusk, and almost always yours alone. Drop off the back into Ano Petralona for a plate and a drink, then the level walk back to Thiseio.
