Caldara di Manziana

The Caldara di Manziana is a volcanic depression with sulfurous springs and marshland on the southwestern edge of the Sabatini volcanic complex. A grove of white birches, royal ferns and alder trees grows among the wetland habitats of this protected natural monument.

Why it matters

The Caldara lies within the Bracciano–Martignano volcanic landscape. Groundwater heated beneath the surface emerges at the spring known as the polla, carrying sulfurous water and gas. Regional law no. 64 of 26 September 1988 recognised the site as a natural monument, protecting roughly 90 hectares of spring, marsh and woodland. The area is also part of the Bracciano–Martignano regional park.

What to notice

At the centre of the depression, the polla produces small bursts of sulfurous water. The water reaches around 27°C. Rainwater filters underground, heats near a buried magmatic body and rises again through the spring. The surrounding habitats include black alder along the fosso della Caldara, royal fern (Osmunda regalis) in wetland areas and a grove of white birch (Betula pendula), whose origin remains debated. Sessile and Turkey oaks, along with wild apple trees (Malus sylvestris), grow in the surrounding woods.

Context and history

The name caldara means cauldron in local dialect, describing the hollow and its bubbling springs. The springs lie within the former Sabatini volcanic complex, whose activity ended tens of thousands of years ago but whose buried heat continues to drive the hydrothermal system. The park authority documents how springs on the Manziana plateau supplied the Aqua Traiana, begun under Trajan around AD 109 to supply Trastevere and later rebuilt as the Acquedotto Paolo. Regional protection in 1988 and inclusion in the Bracciano–Martignano park in 1999 recognised the area's natural and historical value.