The Javadhu Hills (also Jawadhi, Jawadhu Hills) are an extension of the Eastern Ghats spread across parts of Vellore and Tiruvannamalai districts in the northern part of the state of Tamil Nadu in southeastern India.This range separates Vellore and Tiruvannamalai districts. Vellore district lies on the north western side and Tiruvannamalai district lies on the south eastern side of this range. About 50 miles (80 km) wide and 20 miles (32 km) long, they are bisected into eastern and western sections by the Cheyyar and Agaram rivers, tributaries of the Palar. They consist of bluish gray granites, with peaks averaging 3,600–3,800 feet (1,100–1,150 m). The hills are sparsely populated; the majority of the inhabitants are Malayali tribespeople, though other castes are also present. There are many tourist places near Javadhu Hills, e.g., the Beemanmadavu waterfalls. The Indian astronomer Vainu Bappu selected the hills as the site of the Kavalur Observatory (VBO), which began operations in 1967. The towns of Tirupattur, Vaniyambadi and Ambur of Vellore district are located on the north western side and the towns of Chengam and Polur of Tiruvannamalai district are located on the south eastern side .