The list is published on http://www.tripadvisor.com/DirtyHotels-g4, where you can read the sometimes gruesome reviews.

Of the 10 dirtiest hotels, according to the TripAdvisors visitors, the worst 2 are in Turkey, and the places 3-5 are occoupied by London hotels. Numbers 6 and 7 are hotels in Amsterdam, 8 a hotel in London, and 9 and 10 two other Amsterdam hotels.