The Ochil Hills is a range of hills in Scotland north of the Forth valley bordered by the cities of Stirling, Perth and the towns of Alloa, Kinross, and Auchterarder. The only major roads crossing the hills pass through Glen Devon/Glen Eagles and Glenfarg, the latter now largely replaced except for local traffic by the M90 Edinburgh-Perth motorway cutting through the eastern foothills. The hills are part of a Devonian lava extrusion whose appearance today is largely due to the Ochil Fault which results in the southern face of the hills forming an escarpment. The plateau is undulating with no prominent peak, the highest point being Ben Cleuch at 721 m (2,365 ft). The south-flowing burns have cut deep ravines including Dollar Glen, Silver Glen and Alva Glen, often only passable with the aid of wooden walkways.