The most photographed building in London for good reason. The 96-metre Elizabeth Tower — what nearly everyone calls Big Ben, though the name properly belongs only to the 13.5-tonne hour bell — sits at the north end of the Palace of Westminster, looking out over Westminster Bridge and the Thames. Restoration scaffolding came off in 2022 and the gilded clock faces are now back to their original Victorian colour scheme.
UK residents can lobby their MP for a free tour; everyone else can book a paid Saturday or recess-period tour that takes in Westminster Hall (the only major medieval part to survive the 1834 fire), the chambers of the Lords and Commons, and the central lobby. Tours fill weeks ahead in summer.
For free, walk the perimeter: the statue of Boudicca in her chariot at the foot of Westminster Bridge, Cromwell outside Westminster Hall, and on the other side, the Suffragette monument and the cenotaph up Whitehall. Cross the bridge to the south bank for the classic photograph at sunset.