Harpea’s Cave is located in Estérençuby, in the Navarre commune, a few meters from the Franco-Spanish border. It is part of the Aezkoa valley, which is home to some truly amazing caves and landscapes. The name Harpea comes from the Basque word for “the place under the rock”, which aptly describes the location of the cave.

An amazing demonstration of tectonics. Photo: Ángel M. Felicísimo

The cave is not a typical underground cavern, but rather a space between two layers of rock that have been folded by tectonic forces over millions of years. The rock layers belong to the Pyrenees mountain range, which was formed by the collision of the Iberian and European plates. The collision caused the rocks to bend and break, creating folds, faults and fractures.

Harpea’s Cave is an example of an anticline, which is a convex fold of strata, where the center is occupied by the oldest geological layers. The anticline at Harpea’s Cave is made of limestone, which is a sedimentary rock composed of calcium carbonate. The limestone was deposited in a shallow sea about 100 million years ago, during the Cretaceous period. Over time, the limestone was buried under more sediments and subjected to pressure and heat, which caused it to harden and crystallize.

Interior of Cueva de Arpea. Photo: Rutas Por El Monte

The anticline at Harpea’s Cave has been exposed by erosion, which has removed the younger rocks above it. The erosion also created a gap between the upper and lower limbs of the fold, forming the cave. The cave is about 50 meters long, 25 meters wide and 10 meters high. It offers a stunning view of the curved rock layers and the valley below.

Harpea’s Cave is not only a geological marvel, but also a cultural and historical attraction. The cave has been used as a shelter and a refuge by humans for centuries. It has been inhabited by shepherds, smugglers, soldiers and pilgrims. It has also been a site of legends and myths, such as the story of Harpéa, a giantess who lived in the cave and protected it from invaders.

Beauty and amazing geology in one. Photo: Makeip

Harpea’s Cave is a place that will fascinate anyone who loves nature, science and history. It is a testament to the powerful forces that move the Earth’s crust and shape our planet. It is also a reminder of the human connection to the land and its mysteries.