Built on the ruins of a Nabataean castle on a 50-meter rocky outcrop in the city of Sakaka in northwest Saudi Arabia, Zabal Castle consists of a reservoir and four towers that are connected by a single wall.  The castle is believed to have been built 300 years ago, and is open to anyone fascinated by the rich Arab history this region has to offer. This photo was taken by Ziyad Allahim as part of the Colors of Saudi competition.