WINDSOR CASTLE: A NEAR VIEW OF THE ROUND TOWER.
The most conspicuous part of Windsor Castle is the Round Tower, or Keep, which rises from the east side of the Lower Ward. The carefully-laid-out mound on which it is built is 42 feet high, and the battlements 80 feet. The Tower is not absolutely circular, as it measures 102 feet by 95 feet. Until towards the end of the seventeenth century the Keep was used as a prison now its chief end is to provide a point of view whence a dozen counties can be seen. Entrance to the Tower is obtained from the Upper Ward, near the handsome Norman Gateway, on the north side (to the left in our view). The other Gate, on the south, is known as St. George's Gateway. In the Tower is a bell weighing nearly a ton, brought from Sebastopol.
source: The Queen's London : a Pictorial and Descriptive Record of the Streets, Buildings, Parks and Scenery of the Great Metropolis, 1896