Anyone who has played Donkey Kong 64 (or DKC) remembers the factory level(s). My memories lie with Frantic Factory. It has such a tragic backstory the way I depict the series and it has that chill factor that you'd expect from an abandoned (toy) factory. Plus the Mad Jack boss fight was awesome. The level is fun in its own way.

One thing that stands out for me is that it's one of the few levels that didn't have a cheerful score in its level (for most levels, the sad/minor version of it was found in boss fights or at night when it comes to Fungi Forest). Even Gloomy Galleon had a cheerful score when you were racing that seal with DK. But oh well wahtever XP