The Valle de los Caídos, also known as the Valley of the Fallen, is a significant and controversial monument located in the Sierra de Guadarrama. Constructed between 1940 and 1958, it includes a vast basilica carved into the mountain, a towering 150-meter cross, and an abbey. The site, intended as a memorial to those who died in the Spanish Civil War, has been a subject of debate due to its association with the Franco regime and the use of forced labor for its construction. Today, it remains a complex symbol of Spain's history, attracting visitors and scholars interested in its architectural grandeur and historical significance.