Elizabeth Tower

The Clock Tower, otherwise known as Elizabeth Tower, and sometimes erroneously as Big Ben, the name of the great bell that sits within the tower, is a four-faced clock tower that sits adjoined to the Palace of Westminster, in the borough of Westminster, London.

In 1868 the Clock Tower was scaled by Evie Frye, in order to repair the telegraph lines that ran through the building. The tower was scaled a second time later that year, when it was discovered that Templars out of Boston had planted explosives throughout the Palace of Westminster, including one at the top of the Clock Tower.

Reference

 * Assassin's Creed: Syndicate