A city with an ancient civilization that was the crossroads of trade and land routes between Arabia, Mesopotamia, and the ancient world. It is the historical city of Ubar, which was mentioned in many old books and maps. Wadi Dawkah is a natural park of famous Frankincense trees, which is also inscribed in UNESCO World Heritage Site. The wadi in Dhofar region of Oman is a stony, semi desert valley, where the density of frankincense trees spreads across 5 square kilometers.