Tolfaccia, Mountain summit in Lazio, Italy.

Tolfaccia is an isolated volcanic dome in the Monti della Tolfa, in the municipality of Allumiere about 25 km from Civitavecchia, rising to 579 m. Its dome-shaped mass, almost 600 m in diameter, exposes lava outcrops revealed by erosion and ignimbritic deposits. The ruins of the medieval centre of Tulfa Nova stand on the mountain.

The mountain area holds archaeological remains of two settlements from the Final Bronze Age period and burial sites from the Bronze and Iron Ages. These discoveries indicate the region has been inhabited since ancient times.

The mountain summit represents part of the geological heritage of Lazio, with its volcanic structure revealing the historical formation of the regional landscape.

The summit lies in the comune of Allumiere, about 25 km from Civitavecchia. Ruins of the medieval settlement Tulfa Nova stand on the mountain, and the Roman villa della Fontanaccia sits at its foot beside an Etruscan temple. Approach on foot from the surrounding Monti della Tolfa; no road reaches the top.

On the summit stand the ruins of Tulfa Nova, a medieval settlement of the 9th century AD. Two Final Bronze Age settlements and tombs from the Final Bronze Age and the Iron Age were also identified in the archaeological area, and the Roman villa della Fontanaccia lies at the foot of the mountain, near an Etruscan temple.