The eastern region of Kerala consists of high mountains, gorges and deep-cut valleys immediately west of the Western Ghats' rain shadow. 41 of Kerala's west-flowing rivers, and 3 of its east-flowing ones originate in this region. The Western Ghats form a wall of mountains interrupted only near Palakkad; hence also known Pal"ghat", where the Palakkad Gap breaks. The Western Ghats rise on average to above sea level, while the highest peaks reach around . Anamudi in the Idukki district is the highest peak in south India, is at an elevation of . The Western Ghats mountain chain is recognised as one of the world's eight "hottest hotspots" of biological diversity and is listed among UNESCO World Heritage Sites. The chain's forests are considered to be older than the Himalaya mountains.