If you mean the night of the 24-25 October (old calendar) then Lenin was based in the Smolny Institute. This was a former girls school that had come to serve as a base for the Petrograd Soviet Military Revolutionary Committee (MRC) and Second Congress of Soviets. As such it was very much at the centre of the October Revolution (much more so than the more dramatic scenes at the Winter Palace).

Lenin arrived here at around midnight (from Marguerite Fofanova's, where he’d been hiding); in his disguise he initially had difficulty being admitted to the Smolny. Once there, he pushed the MRC to take more aggressive action in taking the Winter Palace and drafted the proclamation of the Provisional Government’s overthrow. He remained in the Smolny during the day of the 25 Oct, which was spent at sessions of the Petrograd Soviet (15:00), where the seizure of power was announced, and the Second Congress of Soviets (22:30). Lenin himself didn’t stay for the entire session of Congress, which ended at 05:00 the morning of the 26 Oct. Instead he retired early to Bonch-Bruevich’s nearby apartment to sleep and draft resolutions for the next day (26 Oct).

Sources: Both Rabinowitch’s The Bolsheviks Comes to Power and Service’s Lenin give fairly blow-by-blow accounts of the October Days. For first-hand accounts though I’d recommend both Sukhanov’s Personal Record and Reed’s Ten Days that Shook the World.