It was King Béla IV who decided to build a fortress here in order to protect Buda from the Mongols, however the castle owes its opulence to the Habsburgs. Outside the palace note the huge turul; the equestrian statue of Eugene of Savoy; King Mathias's fountain; the Lions' Gate, leading to the beautiful interior courtyard; the "war hammer" tower; and the barbican. The palace houses the Széchenyi national library, the Budapest History Museum and the Hungarian National Gallery.