Photo by L0ll0, via Wikimedia Commons (CC0)
🇵🇹 Portugal · São Miguel, Azores
♨ Temperature
40°C
⛰ Altitude
320 m
⚗ pH
6.8
💧 TDS
750 mg/L
🌊 Flow rate
18 L/s
📅 Established
Natural
✓ Verified on 2026-07-22
Caldeira Velha is a natural thermal spring site tucked into the forest-covered interior of São Miguel island, part of the Azores Geopark. Warm sulphurous water at around 40°C emerges from the volcanic rock and flows through a series of pools overhung with tree ferns and ancient laurisilva forest — the surviving Atlantic laurel forest that once covered much of Macaronesia. The pools' turquoise colour comes from the suspended minerals in the water. The site is a protected natural monument, developed with minimal infrastructure: wooden walkways, a small access road, and admission controls to prevent overcrowding. The combination of warm water, green forest canopy, and the sound of the cascade creates a deeply immersive natural environment.
| Sulphur | 35 mg/L |
| Silica | 88 mg/L |
| Bicarbonate | 220 mg/L |
| Calcium | 65 mg/L |
Caldeira Velha sits within the protected laurisilva forest of the Azores Geopark, a landscape that is itself a relic of the ancient Atlantic forest ecosystem that preceded the ice ages. The thermal spring has been known to São Miguel residents for generations as a local bathing site.
The Azorean relationship with their island's geothermal activity is intimate and practical — hot springs are used for cooking (cozido das Furnas), bathing, and heating. Caldeira Velha represents the forest bathing dimension of this culture, distinct from the spa tradition but equally embedded in local life.
The site is protected under the Azores Geopark framework and managed by the regional government. Daily visitor numbers are capped to prevent erosion of the forest floor and disturbance to the thermal pools.
Websitewww.azores.gov.pt
AddressCaldeira Velha, Ribeira Grande, São Miguel, Azores