Bardenas Reales

The Bardenas cover about 42,000 hectares of the Ebro basin where soft clays, gypsum and sandstone laid down in an ancient lake have been eroded by infrequent but violent rain into a landscape of gullies, flat-topped mesas and isolated spires, with almost no vegetation across much of it. Castildetierra, a cone of clay capped by a harder sandstone layer standing about twenty metres, is the most photographed formation. It has been a biosphere reserve since 2000, and it is not empty: sheep have grazed it under ancient rights for centuries, and a large military bombing range occupies a section that is fenced and closed. Unsurfaced tracks cross the accessible part and are used by cars, cyclists and walkers.

What you actually see

• Castildetierra - a capped clay spire that has become the emblem.
• The gully badlands - eroded clay and gypsum with almost no plant cover.
• The flat-topped mesas - harder caprock preserving plateau remnants.
• The grazing flocks - sheep worked under long-standing rights.

When to go

March to May and September to November; summer temperatures exceed forty degrees with no shade anywhere, and winter brings fog and mud. Tracks close after heavy rain, when the clay becomes impassable.

Honest expectations

The tracks are unsurfaced and turn to unusable mud after rain, with closures announced by the park. There is no shade, water or shelter. The military zone is genuinely closed and marked, and straying into it is dangerous.

Nearby

Tudela and the Ebro lie south; the Arguedas cave houses are at the park's edge.