Jame's Develin's Gym
This is a gym design for James Develin's contest, and it is a pretty simple craft. All you need is basic shapes and a bit of skills in the scaling, and rotating portion of designing. This gym would not take very long to make yourself, it was mostly just basic shapes rotated and scaled.
Basic Shapes
These are the basic shapes section on TinkerCad that you would need for the project. There are squares, cylinders and others. They all don't require much effort to work with, so it will be easy to make the gym.
Equipment
The equipment will be fairly simple to make, for the ball, you just get a sphere and scale it smaller or bigger depending on the size comparison between the walls and the ball. The yoga mats are just squares that are scaled into a rectangle using the widing system. The treadmills are a bit more difficult to make, but it is still just basic shapes mixed together. You get two squares and make them both the same size, then scale one of the rectangles smaller than the other one and place it on top of the other rectangle. The stand for the treadmill is just cylinders that are scaled with more height and rotated about 25° in the direction of the rectangles. Duplicate that and place it on another side of the rectangle. Than you can make another rectangle on top, then you are done.
Windows
You just make a square and make it into a hole to imitate the windows at an actual gym, see-through from the inside and not see-through on the outside. It will look better, when you make a similar sized square in the hole and make it transparent and gray.
Finish
Once you have finished your project, you can go do whatever you want with the design. You can submit to James Devilin's contest.