Photo by Angelmanxego, via Wikimedia Commons (CC BY-SA 4.0)
🇮🇹 Italy · Lazio
Photo by Angelmanxego, via Wikimedia Commons (CC BY-SA 4.0)
🇮🇹 Italy · Lazio
♨ Temperature
58°C
⛰ Altitude
—
⚗ pH
—
💧 TDS
—
🌊 Flow rate
—
📅 Established
Documented since Etruscan and Roman times
✓ Verified on 2026-07-28
Piscine Carletti (also known as Acqua Santa) is a group of five to six free natural thermal basins about 2.5 km from central Viterbo, fed by two hyperthermal springs classified as sulphureous-sulphate-bicarbonate-alkaline-earth, emerging at around 58°C and cooling in tiers as it flows downstream. The site has no facilities, no staff, and no entry fee, and is accessible 24 hours a day year-round. Viterbo's thermal springs are documented since Etruscan and Roman times.
| Dissolved residue | 2420 mg/L |
The thermal springs around Viterbo, including the source that feeds Piscine Carletti, have been documented since Etruscan and Roman times, when the area's sulphur waters were already valued for bathing.