Porta Leoni, dating to the 1st century BC, is the oldest Roman gate. It was decorated two centuries later when it seemed too simple for the rich city. He gave access to the Cardo Massimo, which, connected to the Decumano, brought to the Forum, now called Piazza Erbe. Its 15th-century popular name originated from the discovery of a nearby sarcophagus that carried the image of two lions lying down.
As Porta Borsari, it was a small fortress in tuff and bricks with an inner courtyard and, at that time, it was 13 metres high, like the city walls. Today, only the left half of the internal façade remains in a 13th-century building. It was characterised by a square plan with double vaults on the facades, with galleries on the upper floors and two tall cylindrical towers.
Thanks to a meticulous restoration, we can still see, two metres below the road level, the bases of the towers and fragments of the inner courtyard flooring. On the architrave there is a carved inscription with the name of one of the Quattuorviri who built it.