San Millán de Suso is a historic monastery located in the La Rioja region of Spain. It dates back to the 6th century and is known for its early Christian architecture and beautiful Romanesque style. The site is significant for its role in the development of the Spanish language, as it houses some of the oldest written texts in the language. The monastery is part of a larger complex that includes San Millán de Yuso, which was built later. Both sites are recognized as a UNESCO World Heritage Site, highlighting their cultural and historical importance. Visitors can explore the stunning frescoes and ancient manuscripts that reflect the rich heritage of the region.