Siege of Barad-dûr (3434 S.A.) - The final battle of the Second Age.  After winning the Battle of Dagorlad, The Last Alliance of Elves & Men stormed Mordor and laid siege to Dark Tower.

"Then Gil-galad and Elendil passed into Mordor and encompassed the stronghold of Sauron; and they laid siege to it for seven years, and suffered grievous loss by fire and by the darts and bolts of the enemy, and Sauron sent many sorties against them.  There in the valley of Gorgoroth Anárion son of Elendil was slain, and many others.  But at the last the siege was so straight that Sauron himself came forth; and he wrestled with Gil-galad and Elendil, and they both were slain, and the sword of Elendil broke under him as he fell.  But Sauron also was thrown down, and with the hilt-shard of Narsil Isildur cut the Ruling Ring from the hand of Sauron and took it for his own." ~The Silmarillion (Of the Rings of Power and the Third Age)