Looming large over the city center, Guimarães Castle is one of the most complete and best-preserved medieval strongholds in Portugal. Dating from the 10th century, its enormous square keep and the eight crenelated towers that surround it remain a familiar and much cherished landmark. The castle is believed to be the birthplace in 1110 of Portugal's first king, Afonso Henriques, and as such is regarded by many as a national shrine; the much-visited font where he was baptized is kept in the Romanesque chapel of São Miguel, tucked into the western end of the castle. Mass is celebrated here annually on the king's birthday to commemorate the event. The aforementioned keep - known as the Torre de Menagem - reputedly housed an 11th-century Benedictine convent founded by the Countess Mumadona. Visitors can walk the heavy curtain walls and scale the narrow steps to the top of the tower where fine views of the city and the countryside can be admired