"city pass" is almost a necessity in Paris...unless you are the person who loves waiting in line and paying unnecessary admission fees...I forgot to check if someone said this, but yes I consider the City Pass absolutely mandatory in Paris and helpful but not mandatory in London. The Hop on Hop Off Sightseeing Bus that comes with the City Pass is faster and more useful than regular Paris transportation to get to all of the standard tourist areas. The Parisian version is invaluable And a must get.