Big Ben" is the name of the clock inside the famous tower that also forms part of the Houses of Parliament. Its impressive mechanism weighs in at over 13.5 tons, and the pendulum, which beats once every two seconds, is 13 feet long and weighs 690 pounds. The clock was named "Big Ben" after the First Commissioner of Works, and since 1885 a light above it has been lit while the House of Commons is in session. UK residents can schedule a time to climb the clock tower.