Cosmolarium at Castillo de Hornos de Segura uniquely combines medieval fortress heritage with modern astronomical facilities in Jaén province, within the Cazorla, Segura and Las Villas Natural Park. The thirteenth-century castle crowning a rocky outcrop houses an innovative astronomy interpretation center featuring an eight-meter digital planetarium dome, exhibition galleries exploring the cosmos, workshops, and educational spaces. The site takes advantage of its high elevation, minimal light pollution, and extensive visual field to serve as an exceptional astro-tourism destination. Visitors can tour the castle tower, explore the Astronomical Museum, and experience planetarium simulations while enjoying terraces designed for sky and landscape observation, making it the world's only castle dedicated to astronomy.