One Tree Hill is a prominent peak south of Nuwara Eliya town, named for the single tree that once stood on its summit (the tree is gone, replaced by a telecommunications mast, but the name remains). The walk up takes about two hours from the town and gives panoramic views over the town, Lake Gregory, and the surrounding tea estates. On clear days you can see as far as Adam's Peak to the southwest.
The path starts from the road toward the racecourse and winds up through tea estates before entering more open ground. The trail is straightforward and the gradient manageable. The descent on the far side leads through forest toward the lake. Take water and a jacket — the temperature drops significantly as you gain altitude, and cloud moves in quickly.