Oman overlooks the Arabian Sea, the Sea of Oman and the Arabian Gulf. It has terrain encompassing desert, riverbed oases and long coastlines. Wahiba Sands is a region of dunes inhabited by Bedouins. The port capital, Muscat, is home to the massive, contemporary Sultan Qaboos Grand Mosque. The Rub‘ al Khali is the largest contiguous sand desert in the world and it still remains one of the most inaccessible regions on earth. In ancient times the frankincense caravans crossed the desert and built rich trading posts. Since in this desert almost no water there can be found, it is also hardly populated, hence its name Rub Al Khali, the “Empty Quarter”. Ubar, also known as Atlantis of the Sands is the fictional name of a legendary lost city in the southern Arabian sands, claimed to have been destroyed by a punishment by God. The search for it was popularised by the 1992 book Atlantis of the Sands – The Search for the Lost City of Ubar.