West of the coastal areas lies the tableland of central Oman. The Wadi Samail (the largest wadi in the mountain zone), a valley that forms the traditional route between Muscat and the interior divides the Hajar range into two subranges: Al-Ḥajar Al-Gharbī (The Western Hajar) and Al-Ḥajar Ash-Sharqī (The Eastern Hajar). At the same time, mountains in the central region, where the highest of the Hajar are located, are recognised as the Central Hajar. The general elevation is about , but the peaks of the high ridge known as Jebel Akhdar (Green Mountain), rise to more than . Jabal Akhdar is a home of the Arabian tahr, a unique species of wild goat. In the hope of saving this rare animal, Sultan Qabus ibn Said has declared part of the mountain a national park. Behind the Western Mountains are two inland regions, Az-Zahirah and Inner Oman, separated by the lateral range of the Rub al Khali. Adjoining the Eastern Hajar Mountains are the sandy regions of Ash-Sharqiyah and Jalan, which also border the desert.