You are about to travel back to the 4^th century BC, to a hillfort from the second Iron Age that has remained almost unchanged to this day. The hillfort is situated on a small elevation (320 metres; 1,050 ft) overlooking the Salcedo Valley and the municipality of Zalla, which are crossed by the Kadagua River.

The settlement occupies a total area of 4,000 m2 (13,100 sq. ft) enclosed by a wall and an outer moat that runs along the entire southern front of the hill. The Bolunburu Crag provides a natural defence barrier on the north.

The wall is made of masonry, with an average width of 3 metres (10 ft) and a height that may have originally exceeded 5 metres (16.5 ft). The wall had a single gate, located at the southeast end. The houses consisted of simple rectangular huts, built with perishable materials. The few remains of their structure that are still standing belong to the foundations. In addition, other enclosures that served as sheds, workshops and warehouses have been identified.

Witchcraft legends

The Bolunburu complex allows us to understand what the day-to-day life in the hillfort was like. Today we know that its inhabitants practiced a diversified economy based on livestock farming, subsistence agriculture (mainly cereal and legume crops), the harvesting of wild products, and iron metallurgy. Many charred acorns have been found inside the houses. But perhaps the greatest peculiarity of the place is the discovery of abundant hand mills made of local sandstone.

Furthermore, the toponymy surrounding the hillfort is noteworthy, as it mentions witches and wizards—a colloquial demonym for the people of the municipality of Zalla. These witchcraft legends are perhaps linked to the inhabitants of the hillfort and find their greatest expression in the so-called Campa Las Brujas (The Witches' Field), where it is said that they used to meet and dance by the river.

The hillfort is located very close to the Bolunburu recreational area and La Mella historical monuments, both washed by River Kadagua.