Castillo de Hornos

Castillo de Hornos is a medieval fortress perched above the town of Hornos, in the province of Jaén, inside the Sierras de Cazorla, Segura y las Villas Natural Park. It sits on a rocky outcrop overlooking the Tranco reservoir, an artificial lake that submerged the valley once visible from the castle walls.

Where does this fortress come from?

The site passed into Christian hands in 1239, when it was conquered by Pelayo Pérez Correa, one of the most prominent masters of the Order of Santiago. The location then became part of the commandery of Segura de la Sierra, under the diocese of Cartagena. The structure visible today was built at the turn of the 13th and 14th centuries, on top of an earlier Muslim fortification. That layered history — a Muslim base topped by a Christian stronghold — explains the castle's strategic position: whoever held it controlled the mountain passes and routes through the Sierra de Segura.

What will you find inside?

The biggest surprise for many visitors is that Castillo de Hornos doesn't function as a conventional history museum. Its interior houses the Cosmolarium, an astronomy outreach center with a planetarium and a sky interpretation space. Alongside the walls, towers and valley views, visitors find exhibits on the cosmos, the planets and the history of celestial navigation. It's an unusual pairing: medieval defensive architecture and a modern science education venue under one roof.

From the outside, the castle impresses through its setting alone. Hornos is one of the most photogenic villages in Jaén province, clinging to the edge of a cliff above the waters of the Tranco reservoir. The panorama of the lake framed by the Sierra de Cazorla, Segura y las Villas mountains is as much of a draw here as the building itself.

How to get there and when to visit?

Hornos sits at the heart of the natural park, in a mountainous, sparsely populated region — the town has fewer than 600 residents. Access is via local roads winding through the Cazorla and Segura mountain ranges, which is an attraction in its own right: the route passes through forests and viewpoints over the Tranco reservoir, which also touches the municipalities of Santiago-Pontones and Villanueva del Arzobispo.

Given the mountain climate, spring and autumn are the best times to visit, when temperatures are mild and the Sierra de Cazorla landscape shows its most vivid colors. In summer, evening astronomical observation sessions at the Cosmolarium draw crowds, offering a chance to see planets, nebulae and galaxies from a spot with minimal light pollution.

Why stop here?

Castillo de Hornos is more than a dot on the map of Jaén's castles — it's a gateway to one of the quietest corners of the Andalusian mountains. The combination of a historic stronghold, sweeping views over the Tranco reservoir and an unexpected astronomy center makes a visit here different from a standard castle tour: it's both a lesson in regional history and a chance to look up at the sky.

Frequently asked questions

Is Castillo de Hornos open to visitors? Yes, the castle operates as the Cosmolarium center and welcomes visitors both during the day and for evening astronomical observation sessions.

What can you see from the castle walls? A sweeping view of the Tranco reservoir and the surrounding Sierra de Cazorla, Segura y las Villas mountain ranges.

When was the castle built? The current structure dates to the turn of the 13th and 14th centuries, built over an earlier Muslim fortification shortly after the Order of Santiago conquered the area in 1239.

Is there anything else to see in Hornos besides the castle? The town itself, home to fewer than 600 people, is considered one of the prettiest villages in Jaén province — worth a walk through its narrow streets and a stop at the viewpoints over the Tranco reservoir.