Bagnaccio is the name of ancient thermal baths that are still in use 8 km northwest of Viterbo, in the Lazio region of Italy. Viterbo is also known as 'La città termale' aka the Thermal City because of the many natural hot thermal springs that dot the nearby countryside.
The Bagnaccio baths are located directly on what was the ancient via Cassia on the road to Montefiascone while the via Cassia now runs about 1 km east of the baths. The site was and is still marked by the ancient Roman ruins of Bacucco, a small baths complex on the same narrow unpaved road 'strada bianca' and these baths were recorded in designs by Michelangelo (Lille). Regular bathers at Bagnaccio pay dues of 12 to 18 euros to keep the pools clean, although day passes are also available.