I always wondered what some locations are actually supposed to be. For MM1 we can tell now because of Powered Up which showed us for example that Cut Man stage is actually some sort of forest.

But what about later games?

We can pretty much say for 100% certainty that Wood Man stage is in a forest and Metal Man stage in a factory. But many of the others are open to assumption. If we think realisticly, where could the robot master stages take place?

My guesses/ideas are:
Heat Man: inside active volcano
Bubbe Man: a dam
Quick Man: a secret military base
Flash Man: crystal caves
Crash Man: ?
Air Man: ?

Top Man: a greenhouse
Hard Man: a canyon
Snake Man: an ancient temple
Spark Man: electric plant

...