The seventh world of New Super Mario Bros. ULTIMATE is factory and mountain themed, mainly factory. It is ruled by Ludwig Koopa.
Nuclear Factory 1
The first level of Nuclear Factory takes place inside a waste-filled factory. It features nuclear waste barrels that Mario can pick up and throw, but Broozers in the course can pick them up, too. If Mario touches any form of waste, he will die. Mario begins on a catwalk made of pipes, where he must climb down, avoiding Broozers and flows of waste. Near the end of this section is a blocked bridge. Mario must use a Bob-omb coming from a blue pipe to ingite a barrel of waste and use it to blow up the blockage. After here is the checkpoint and a section with Thwomps and Rhomps that can crush Mario. Mario must avoid several waste flows and use a small platform at the end to ride on one. At the last section, Mario must ride a swinging girder that will take Mario to the flag.
Nuclear Factory 2
This section is more mountain themed. Mario starts on a high cliff with some barrels. Mario must use the barrels to blow up a wall that will lead Mario to a section with a small boat that will lead him across a lake of waste. Along the way, Mario must make sure that no more than five enemies get on to the boat as they fall from the sky, otherwise it won't move. If eight fall, it will sink. Mario must use some barrels to blow up walls on the way. After this part is a green pipe leading him to a section with mushroom platforms in waste. Mario must hurry, as the mushrooms decompose quickly. After one decomposers, Mario must jump at the right angle to reach a hidden pipe if he wants to reach the secret exit. The flagpole is right after here.
Factory Secret 1
This level is openable by getting the secret exit in Nuclear Factory 2. It leads to the first tower.
Nuclear Factory 3
Factory Ghost House
This dark ghost house is built, unfortunately, right on a stream on nuclear waste. This waste brings light to most of the beginning and end, but the maze of doors in the middle is dark and scary. Fortunately, a Glow Block is found near the stream, and several others, too.