Castle Construction is the second course in Super Mario 64: New Castle. It is found in the door with a Thwomp on it and needs one power star to get into. To find the door, go straight from the entrance to Peach's castle and then a little bit to the left.
Star 1: Foreman Thwomp's Monstrous Contraptions
This course is a large tower which is slowly being constructed and deconstructed by mechanical hands. Mario must climb to the top, dodging several Thwomps. At the top, Mario finds a giant forklift with a huge blue stone on the top. Upon messing with the forklift controls to bring it down, Mario finds out that the blue stone is Foreman Thwomp! Defeat Foreman Thwomp by tricking it to crush the fragile, cracked parts of the tower. Eventually the whole tower will fall because of how much has been destroyed. Foreman Thwomp will give Mario a star.
Star 2: New Fort
The tower has been re-built this time. In fact, it is better built than before. It is almost complete! Mario needs to climb the even-taller fort to find a block. Mario must push the block off the tower, which sets off a chain of events to built the entire tower! Foreman Thwomp appears and thanks Mario, giving him another Star.
Star 3: The Extension Convention
The tower is now building a new extension to the left! Mario has to climb halfway up the tower and take the side route along the extension to find the Star.
Star 4: Futuristic Eight Red Coins
The tower now has mechanical high-tech airships floating around it, ready to ferry guests around the tower. Mario needs to climb to the top and jump on one. He then has to find all the red coins on them. The star that appears when he gets all eight is at the beginning of the course.
Star 5: Bowser's Airship Invasion
Bowser's airships have taken over the tower and blasted down the other airships. These ones are protected with large shields. To land on the one with the star, Mario needs to grab onto a rocket at the bottom of the tower that will propel him above the airship's shields.
Star 6: Shoddy Construction
A new extension is being built on the right side of the tower. However, it is not very powerful. Mario has to use the rockets to get to the top of the tower, and then do a ground pound from the very top onto the extension, destroying it. A star was hiding in it.