Guadalajara is a city and municipality in Spain, located in the autonomous community of Castilla–La Mancha. It is the capital of the Province of …Guadalajara is a city and municipality in Spain, located in the autonomous community of Castilla–La Mancha. It is the capital of the Province of Guadalajara. Lying on the central part of the Iberian Peninsula at roughly 685 meters metres above sea level, the city straddles the Henares River. As of 2018 it has a population of 86,222 which makes it the region's second most populated municipality.