Дол Гулдур
The Nazgûl besieged Minas Ithil, a fortress located in a valley in the Ephel Duath once belonging to the kingdom of Gondor, and, after two years, captured it and acquired its "palantír" for Sauron. The city thereafter became Minas Morgul, the stronghold of the Nazgûl, and the valley was henceforth known as Morgul Vale (Imlad Morgul). Sauron returned from Dol Guldur in Mirkwood to Mordor late in the Third Age and declared himself openly. He sent two or three of the Nazgûl to garrison Dol Guldur.