Ojo Guarena

Ojo Guarena is a karst system beneath the Merindades of northern Burgos with well over a hundred kilometres of surveyed galleries on several levels, among the largest in Europe and a natural monument since 1996, formed by the Guarena river which disappears underground at one end and re-emerges at another. Its most visible point is the hermitage of San Bernabe, a chapel built into a cave mouth in the hillside with a stone facade closing the entrance and a painted interior of the sixteenth and eighteenth centuries showing the saint's life and the cave itself. A short guided route runs from the chapel into the first galleries, where prehistoric remains and later use are explained. Rock paintings in the Palomera cave have been dated to about 10,000 years ago, and around 400 cavities are known in the area. The wider system is closed to visitors and reserved for research and caving.

The landscape

• The San Bernabe hermitage - a chapel built into a cave mouth in the cliff.
• The painted interior - sixteenth and eighteenth-century wall paintings.
• The guided gallery - a short route into the first chambers.
• The karst landscape - sinkholes and the disappearing Guarena river.

When to go

April to June and September to October; the hermitage and guided visits keep seasonal hours, generally opening in spring and closing in autumn with reduced weekend service between. Booking is advisable.

Things to know

Only a small part of the system is accessible and the guided route is short. Opening is seasonal and limited, with places capped. Northern Burgos is remote and public transport does not reach it.

Nearby

The Merindades villages and the Ebro gorge lie around; Burgos is ninety kilometres south.

Key facts