- The castle of Ten Towers also has a tower called the Widow's Tower.
The Widow's Tower is one of the five major towers of Harrenhal. Its original name was lost with the death of Harren the Black in the burning of Harrenhal during Aegon's Conquest. It has since been renamed the Widow's Tower. There is a stone bridge that connects it to Kingspyre Tower.
King Jaehaerys I Targaryen settled his widowed sister, Queen Rhaena Targaryen in Harrenhal in 56 AC since apart from the Tower of Dread where the impoverished Lord Towers resided it was empty. Rhaena, who lived in the Widow's Tower, became friends with poor Lord Maegor Towers, and she took care of his household after their lord's passing in 61 AC. 
A Clash of Kings
While Lord Tywin Lannister rules the castle, the Brave Companions, a sellsword company from the Free Cities, are housed within this tower. The Brave Companions hold their prisoners in the large, one-room cell beneath the Widow's Tower.