The broken tower is located near the lichyard and the First Keep. Its stones are loose, as their mortar has turned to ash. The top third has collapsed inward and the lower level is full of fallen stone and ruined beams. The summit is jagged.
The tower was once the tallest watchtower of Winterfell, but it was ruined by a lightning strike at least a century before the birth of Eddard Stark and was not rebuilt. Lord Eddard sometimes sends ratters into the lowest level to clear out vermin. Bran Stark, Eddard's middle son, enjoys climing from the First Keep to the broken tower so he can feed crows from the eyrie atop.
A Game of Thrones
Since he is supposed to leave Winterfell and accompany his father, Lord Eddard Stark, to King's Landing, Bran Stark decides to climb to the top of the broken tower one last time. While climbing the First Keep, however, he discovers Queen Cersei Lannister and Ser Jaime Lannister cavorting within. Jaime tosses Bran from a First Keep window, crippling the boy.
A Clash of Kings
A Storm of Swords
—thoughts of Bran Stark
Once Bran had known every stone of those buildings, inside and out; he had climbed them all, scampering up walls as easily as other boys ran down stairs. Their rooftops had been his secret places, and the crows atop the broken tower his special friends.—thoughts of Bran Stark