Caldeira Velha

Caldeira Velha is a natural thermal site on the northern slopes of the Água de Pau / Fogo volcanic massif in Ribeira Grande, São Miguel, in the Azores. Set within dense laurel and fern forest, it centres on a warm waterfall that feeds a series of stepped, iron-rich bathing pools.

The thermal pools and waterfall

• A waterfall drops through the forest canopy into a bathing pool.
• Several stepped pools follow, ranging from cooler at the waterfall to warmer where geothermal water enters.
• Reported water temperatures span roughly 24–38 °C, with an average around 34 °C; the warmest pools sit near body temperature while the waterfall pool is cooler.
• The waters are rich in iron, giving the pools and rocks their characteristic ochre colouring.

A protected nature monument

The springs are heated by the geothermal reservoir of the Fogo volcano (Lagoa do Fogo volcanic complex). The area is classified as a Natural and Regional Monument and shelters great biological diversity, including tree ferns, acacias and bamboo.