The Palacio del Infantado is the best reason to visit Guadalajara, and one of the finest buildings of its era in Spain. The exterior is covered in diamond-shaped stone bosses — a Mudéjar-influenced decoration technique that gives the facade an almost hypnotic geometric texture. Walk around to the courtyard and the effect changes entirely: a two-storey arcade of intricately carved arcades and ogival arches opens around a central space that feels both Gothic and Moorish at once.
The palace now houses the Provincial Museum of Guadalajara, with collections of local archaeology, medieval art, and a room of Spanish Civil War documentation including material on the Battle of Guadalajara. The museum is good; the building is the point.