The Celio is the hill that should be overrun and somehow isn't — it touches the Colosseum on one side and stays empty on the other, a wooded ridge of churches and gardens that the crowds never bother to climb. That gap is the whole point.
A little over three kilometres, best in the morning. From Colosseo, climb into Villa Celimontana, a park of palm avenues and an Egyptian obelisk where the loudest sound is a dog. Then Santo Stefano Rotondo: one of the oldest round churches anywhere, ringed inside with frescoes of martyrdoms painted in detail you won't forget. It is rarely more than half full.
Walk down the Clivo di Scauro, a Roman lane still spanned by its brick buttresses, past the basilica of Santi Giovanni e Paolo and the painted Roman house beneath it. Then San Gregorio Magno, the church that sent monks to convert England, behind its baroque stair.
End on the western slope above the Circus Maximus, the green hollow where the chariots ran, and pick up Metro B at Circo Massimo.
