See You at Munden's
Eventually my brother discovered that Munden's was a bar in a city at the nexus of realities, Cynosure. Cynosure was the setting of the comic book Grimjack, published by First Comics and created by John Ostrander and Tim Truman, both still active in comic books last I checked. At the time my brother discovered all this First Comics was either out of business or about to go out of business, though over the years (and with the help of eBay) he was able to get a complete collection of Grimjack comics. I've inherited that box of comics and I've also been purchasing the collected versions from IDW, though they aborted the publication halfway through and have begun again with smaller sized omnibus editions. I've yet to do a complete read of Girmjack but I've been thinking about the setting of Cynosure.
Cynosure is a "pan-dimensional city", one where multiple realities meet. You could be walking down a street that is straight out of Lankhmar, take a few turns and find yourself walking down a street that would fit in perfectly in Mos Eisley Spaceport or Coruscant. On one block magic and technology might work perfectly while on others one of those might be partially or completely limited.
It's a tough concept to fully wrap your brain around, one that I think requires some suspension of disbelief. I'd always try to figure out how such a city works. How tightly together is the city? Do people use it to travel from one dimension to another? What do the inhabitants of the component cities, the parts not part of Cynosure, know about Cynosure?
That said, it makes for an awfully neat place for gaming. I think it would be especially appropriate for games like Dungeon Crawl Classics where other planes and dimensions are an expected part of the game and many of the source materials make use of such concepts.
To do a full-fledged game in such a city I would think you would need a game which can handle genre crossing easily. On the crunchy side games like GURPS or Hero could certainly handle such things. If one is more on the storytelling side of the axis various incarnations of Fate would certainly work well. Grimjack features scenes where its protagonist, John Gaunt, uses his knowledge of the city to know just where to go to make bullets not work against him - a great example of the sorts of actions taken with Fate points.
However, one would not need to do a full game in such a city - it certainly could be used for an interesting adventure in a game like Dungeon Crawl Classics where adventurers encounter such a fantastic city.