Amon Lanc

Amon Lanc, the Naked Hill, was a hill in the southern parts of Greenwood the Great. It had once been the capital of the Woodland Realm of the Silvan Elves under Oropher in the Second Age.
Around a millennium after his defeat, Sauron came to Amon Lanc and reoccupied Oropher's abandoned stronghold. The hill and fortress were then together called Dol Guldur, and the wood in which it stood became known as Mirkwood.
In the Fourth Age, southern Mirkwood became known as East Lórien and with Dol Guldur cleansed of evil, Amon Lanc became part of it.