In a strategic place on the banks of the Pisuerga, stands the Simancas castle from the 15th century, considered one of the most important in Spain, and an emblematic monument of the town. The fortress, ordered to be built by the admirals of Castile, was later transferred to the Crown and since the time of Philip II, has housed the General Archive of the Kingdom. It preserves an interesting collection of documentary gems on monarchical rights and imperial management. It currently houses the General Archive of Simancas, where important State documents are stored, in addition to being used as a research center. In the town center one can also admire the altarpiece and the valuable silverware kept in the parish church.