My friends, there exists premade maps of labyrinthian proportions that twist and turn, with multiple larger and smaller rooms, shortcuts and hidden passages, and yet still in a format that encourages a natural flow through the area.

It's called IKEA and you can use their floor layouts to trap your players in an inescapable hell.

A good idea, but what came to mind: You enter a small well lit cave. The walls have assorted moccasins, chopines, poulaines, and other footware spiked to them. A goblin in a colored shirt runs out and greets you in a croaking voice. "What can I help you with today?"

A group of pale, unhealthy humanoids approach. There are armed with Orange Julius and wearing JNCO jeans

Roll for initiative

I'm GMing Cyberpunk right now. Battlemaps are reskinned screenshots of Google Maps or floorplans of actual businesses.

I still burn tens of hours translating them into a gridded map, but still. It is sort of easier.

Using airport maps could give you really nice layouts too.

I'm making a campaign set in fantasy Vegas, so I took the floorplan of a casino and made it into a map of the city.

Reminds me of Magic Maze, a boardgame in which players play a Barbarian, a Dwarf, an Elf and a Magician who lost all of their gear in battle and now resort to robbing a shopping mall so they can go on their next adventure.

The TRPG "Troika!" has a module that is basically exactly this called "Get It At Sutlers"

It just generates a dungeon crawl contained entirely within a department store by the name of Sutlers

I also use public school maps, zoos, and amusement parks

Hell on earth, perfect

Sawgrass Mills. South Florida FTW

That mall map looks like a map of a later Doom 2 level. Monster closets everywhere!

It looks like a Pegasus or a stegosaurus