The castle hill dominates Burgos from above the old town, and the views from the top justify the twenty-minute climb. The castle itself was one of the great fortresses of medieval Castile but was almost entirely destroyed in 1813 when the retreating French blew up the powder magazine. The ruins that remain give little sense of the original scale, but the excavated underground cisterns and tunnels are interesting.
An underground museum within the excavated castle gives a good account of the site's history, from its origins as an Iron Age settlement through its role as the seat of the Kingdom of Castile and its gradual decline after Madrid became the capital. The views over the city and the meseta beyond make the climb worthwhile even without the museum. Free entry to the castle grounds; small charge for the underground museum.