Simplify the following text for a Grade 7 native English-speaking person.
Original: Now Big Ben is often used , by extension , to refer to the clock , the tower and the bell collectively , although the nickname is not universally accepted as referring to the clock and tower .
Simplified: Big Ben is the nickname of a bell that rings in the clock tower at the northern end of the Houses of Parliament in Westminster , London , England . Officially , the tower itself is called the Clock Tower , Palace of Westminster .