Oh, and pre-Revolution Havana.
Berlin?
Legal prostitution, yep.
There are several casinos scattered through the city.
Drugs plentiful in certain areas of town.
Murder for hire? Hmm - probably could find some mafia types there, but if you do it yourself, there is no death penalty in Germany, and the sentences are pretty light compared to the US.
Now, the talking in theaters - that is the deal breaker. They don’t do that there.
San Francisco.
Maybe not in the top seven, but since the gays run the town, it deserves consideration. 
Everyone thinks of Bangkok, but really, as far as Thailand goes, Pattaya is definitely the one that qualifies. It is Sleaze Central.
I would not include Singapore, at least not in recent decades. Over here, it has a very strait-laced reputation. It’s really a modern place and as such, a good first stop for Westerners to ease into Asia. Ironically, a few years ago, the Singaporean government finally extended bar hours and even legalized table-top dancing, which had been strictly outlawed, at about the same time that the Thai government started cracking down on bar hours in Bangkok. I would put Hong Kong ahead of Singapore even though, yes, I think much of the crime there now is financially related. (No one cares about tradition anymore. 
)
I also nominate Phnom Penh. A fascinating city for a weekend visit, but there is some truly evil sleaze around.
Singapore? Singapore is a shopping mall with an army.
However, prostitution is legal there in some forms. It’s certainly not as exposed as it is some places in Thailand or even Viet Nam, but it does exist. No drugs though. One Vietnamese national was executed in Singapore for smuggling drugs from (I think) Burma to Malaysia, but stupidly transitioned his flight in Singapore and was unlucky enough to be caught there. Gambling exists I think, but not to the extent of other Asian capitals. Smoking and drinking are legal, but heavily taxed. You can’t buy chewing gum at all, though I’ve heard you can bring it with you.
Heinlein’s description of “Sin” city seem badly out of date.
Count me in as another person scratching his head at the inclusion of Singapore. Back during the 60s and 70s, it was probably sinful, but it is very safe and clean now. I go there every couple of months for R&R and even the taxi drivers are honest.
Great quote. May I steal it some time?
As for the OP, I haven’t been around much, even in Asia. Once, when I was back in the US and word got around in my workplace that I had been working recently in Taiwan, an older fellow kind of sidled up to me and started asking, “so, uh, over there where you were, it’s, uh, kind of like sin city over there, uh?”, all shifty-eyed, like a really sleazy Boomhower. Didn’t occur to me 'til later that, once again, someone had misheard and thought I had been working in Thailand. If I’d known, I’d start telling him all about the goldfish and ping pong balls, but too late.
If that’s the case I’m thinking of, he was taking them from Vietnam to Australia, which he and and his family were citizens of. And the only reason the poor bastard was doing it was because his lowlife brother had gotten into a lot of trouble with Vietnamese loan sharks or other shady types in Australia, and by transporting these drugs this one time, they were going to forgive all or part of his brother’s debts. Hope the brother appreciated the effort!
Looking up Glory Road, I see it was published in 1963. I guess Singapore was still a little wild at that time. I have an American friend who was stomping around the city-state circa 1975-77, and it sounds like it was still not much reformed then.
Anyone here remember Flashman’s escapades in Singapore in Flashman’s Lady?
It is not uncommon for us Thailand-based expats to be asked what it’s like living on an island that’s threatened with imminent Chinese invasion.
Trade ya.
Definitely not Macau. I saw more “sin” in the three weeks I spent in Vegas than in the year I spent in Macau. Heck, in the casinos over there they don’t even normally serve you alcohol, but push around carts of tea and milk!
I never even saw much sinfulness going on in Hong Kong. I know it has a reputation for the whole “World of Suzie Wong” thing, but as far as I could tell that’s mostly long gone. Hong Kong is all modern and clean and long working hours as far as I could tell.
I’m going to add Tijuana as well- having visited there, I have to say it’s exactly like it is in the movies- and add Casablanca, which apparently still has a reputation as One Of Those Places where you can get anything if you talk to the right people, with the right mix of Foreign & Exotic thrown in for good measure.
Singapore had a fairly wild reputation right up until the '60s, IIRC, although as has been said it’s a fairly strait-laced (excuse the pun) place now and Bangkok appears to have taken over its former role, at least in popular imagination.
Riga seemed pretty quiet, when I was there. A guy in Vilnius kept trying to sell us Soviet era gasmasks from under his trench coat, though.
We must’ve not been in the same neighbourhoods 
Back in the mid-90s, my roomates and I were watching Escape from New York on TV, and one of them kept swearing up and down that several scenes were just like Russia when he had been living there just recently.
I have to agree. You can get anything you want in Hong Kong, but you can get anything you want pretty much in any town in the world if you know who to ask. I love Hong Kong, but it’s not what I would call sleazy or bawdy. Maybe in the old days…
I recently read a list of the top, sinful party cities in the world. New Orleans was the only U.S. city to make the list coming in at number seven IIRC. I can easily see that after living there but I was a little surprised that Las Vegas wasn’t included as well.
Lagos.
Colón, Panama. It is a port city at the north end of the Panama Canal. It is known as a hotbed for smugglers and tourists are strongly discouraged from visiting, due to the number of pirates (literally), banditos, and other “unsavory” charcters.
Prostitution is legal in Panama and the drug trade is significant due to its proximity to Columbia (smuggling is huge, and it’s not difficult to buy an A-47 if you want one). Being such a key port for trade you can find anything there.
It used to be a hotspot of cabarets and theatres. but during a time of upheaval in the 1960s, it declined rapidly, rich merchants moved to the U.S. or U.K. or into gated communities outside the main city. Unemployment has been round 40% for decades and the poverty rate is obscenely high. Unlike most of the country (where violence against tourists is rare), violent crime there is much higher in that region.
It’s probably comparable to that part of Tatooine where Luke Skywalker met Han Solo.
ETA: I also wouldn’t call it a “party” city, it’s more the seedy underbelly that supplies the party cities.
You got that right! I was in the Lisboa Casino once in Macau, and the only place you could get a drink was at a small bar counter in the basement. There were also slot machines in the room, but you could not take your drink over to the slots. If you wanted to drink, it had to be at the bar.