The Nizwa Fort is a massive castle in Nizwa, Oman. It was built in the 1650s by the second Yaruubi Imam,  It is Omans most visited national monument. The fort was the administrative seat of authority for the presiding Imams and Walis in times of peace and conflict. The main bulk of the fort took about 12 years to complete and was built above an underground stream. The fort is a powerful reminder of the towns significance through turbulent periods in Omans long history.