You may spot Alcala Cathedral from a distance before you actually find this amazing building. Pop inside if the doors are open or just appreciate the facade from outside.
When you've spent some time at this Alcala de Henares principal church, why not make your way to Parque Europa, University of Alcala, and Convent of Las Clarisas de San Diego? They're not too far from Magisterial Cathedral of Saints Justo and Pastor and also a favorite with many tourists.