I guess London is the original to have these double-decker buses for tours. Other famous cities like San Francisco, Paris or even here in Cologne have these buses too. The so called hop-on, hop-off tours. Remembering our tour in London, it wasn't such a good idea to ride one actually. We got stuck in traffic jams! It was terrible! There were just too many of them that they could barely move. Better learn to get acquainted with their tube, faster way to go somwhere.