the Eastern Region of the Emirate of Abu Dhabi, on the United Arab Emirates' border with Oman, adjacent to the town of Al-Buraimi. It is the largest inland city in the United Arab Emirates, the fourth-largest overall (after Dubai, Abu Dhabi, and Sharjah), and the second-largest in the Emirate of Abu Dhabi. The freeways connecting Al-Ain, Abu Dhabi, and Dubai form a geographic triangle in the country, each city being roughly 130 kilometres (81 mi) from the other two. A one and a half hour drive from Abu Dhabi city, Al Ain is one of the world's oldest permanently inhabited settlements, and a UNESCO World Heritage Site. Al-Ain is known as the "Garden City of the Gulf" due to its greenery, particularly with regard to the city's oases, parks, tree-lined avenues and decorative roundabouts, with there being strict height controls on new buildings, to no more than seven floors, and according to one author, an oasis around Al-Ain is the most important in the Arabian Peninsula.