"Shocked and horrified," summed up an Australian traveller's review of the Central Hotel am Dom in Cologne, Germany.
Following publication of the lists earlier this year, Times reporter Stephen Bleach was sent to spend a night at the Cromwell.
Bleach admitted he was somewhat sceptical of anonymous user reviews, but he quickly discovered some common ground with TripAdvisor's faceless critics: "Sitting in room 406 in the grey light of dawn, I have one argument with the TripAdvisor verdict. I became a squalor connoisseur in my backpacking days, and I reckon this isn't just the worst hotel in Britain. I think it might be the worst hotel in the world," he wrote.
Some cities fared worse than others, with hotels in New Delhi and Paris each taking eight of the 10 spots on the list of 'dirtiest' hotels in India and France respectively.
No hotels in New Zealand, Australia or the Pacific were mentioned on the lists.
The 'dirtiest' hotel in the US, New York's Hotel Carter, has been reviewed 804 times on TripAdvisor - 657 of the reviewers gave it two stars or less.
A reader who stayed there last month gave it a damning review under the heading: "Discover new diseases during your stay - For free!!"
"I wouldn't bother staying at Hotel Carter even if you paid me. My safety and health are worth much more than any price," they wrote.
"I would even consider sleeping outside with the homeless, for a cardboard box must be safer than this place."
Ten hotels are mentioned in each regional category bar Germany, which has just three.
"We looked everywhere, honest. But our members tell us there aren't that many dirty hotels in Germany," the editors at TripAdvisor wrote.
Some of TripAdvisor's 'dirtiest hotels in the world':
Asia (Pacific):
1. First Hotel, Bangkok, Thailand
2. Hotel Grand Central, Singapore, Singapore
3. The Imperial Hotel, Hong Kong, China
France:
1. Hotel Merryl, Paris, France
2. Hotel Bristol Republique, Paris, France
3. Hotel Lebron, Paris, France
Germany:
1. Hotel Modern, Munich, Germany
2. Central Hotel am Dom, Cologne, Germany
3. Ludwig Hotel, Munich, Germany
India:
1. Centaur Hotel, IGI Airport, New Delhi, India
2. Hotel Regent Continental, New Delhi, India
3. Ashok Hotel, New Delhi, India
Italy:
1. Hotel Nizza, Rome, Italy
2. Hotel Anglo Americano, Rome, Italy
3. Repubblica Hotel, Rome, Italy
Spain:
1. Playamar, S'illot, Spain
2. Catalonia Gardens, Salou, Spain
3. Rambla & Catalunya Hostel, Barcelona, Spain
United Kingdom:
1. Cromwell Crown, London, England
2. Corbigoe Hotel, London, England
3. Nanford Guest House, Oxford, England
United States:
1. Hotel Carter, New York City, New York
2. Continental Bayside Hotel, Miami Beach, Florida
3. New York Inn, New York City, New York
* For the full lists see TripAdvisor.
