Sightseeing by bus is a must-do in London and the city offers 3 different hop-on, hop-off tours. Hop-On, Hop-Off Bus guarantee you the best prices on these tours as well as great bus + attraction saver combos. Most London Hop-On, Hop-Off Tours include a river cruise and a walking tour. but there is also a fantastic low priced option for those who just want to explore by bus.