This is not a tourist attraction and may not offer toilets, parking, or other services. Visit at your own responsibility.
Castro de Bolunburu is one of the most important Iron Age archaeological sites in Bizkaia and offers visitors a fascinating glimpse into life in the Basque Country before the Roman conquest. Located on a hilltop near Zalla, in the Enkarterri region, the settlement occupies a strategic defensive position overlooking the surrounding valleys.
For centuries, the site remained hidden beneath a large pine forest until a wildfire in 1998 unexpectedly led to its discovery. After the fire, cleaning work revealed the remains of a defensive enclosure surrounded by an embankment. Archaeological surveys soon demonstrated the enormous historical potential of the site, and systematic excavation campaigns have been carried out since 2002.
The Castro de Bolunburu was a fortified settlement from the Second Iron Age and is believed to have been inhabited between the 4th century BC and the 1st century AD. The people living here probably belonged to the ancient tribe of the Autrigones, one of the pre-Roman peoples of northern Iberia. Their way of life was based mainly on livestock farming, agriculture, and iron metallurgy. Archaeological findings show that they cultivated cereals and legumes, while also gathering wild foods such as acorns. In fact, numerous carbonized acorns were discovered inside the houses during excavations.
Researchers also uncovered many circular hand mills within the settlement, suggesting that grain processing played an important role in daily life and possibly even in local trade with neighboring communities.
The easiest access starts from the parking area of the Bolunburu Recreational Area. A little further on, you need to cross to the other side of the Cadagua River via the wooden bridge and follow the marked signs that lead uphill over the motorway tunnel toward the mountain. Continue following the red painted markers and you will reach the site after approximately 2 kilometers of ascent.
Updated on May 11, 2026
