Guinea pigs are intelligent and active creatures that will get bored and overeat if they don't have enough to do. To keep your pig happy and healthy, give him a nice, soft corner for sleeping, a space for food, several PVC pipes to crawl through and plenty of toys to play with. All of that will require a large, custom-made cage.
Measure the amount of space you would like to provide your guinea pig. Purchase thick sheet plastic and several indoor/outdoor carpet remnants or samples that you can place side-by-side or stitch together in the cage. Lay the carpet pieces on top of the plastic to prevent messes seeping through onto your table or floor.
Buy several wire mesh grids--the kind you use to make storage cubes--and plastic or wire ties. (Garbage bag ties are good, as are fencing ties.) Arrange the mesh grids into a rectangular shape, with the edges about 1 inch inside the carpet flooring. Use the ties to connect and anchor the mesh grids into place. Be sure that the excess ends of the ties are on the outside of the cage so that your guinea pig doesn't chew on them.
Purchase an under-the-bed rectangular storage container, and fill it with flannel material. (An old nightie or pillowcase will do fine.) This will be your guinea pig's bed.
On the opposite side of the cage, put a small cat box filled with newspaper pulp. Train your pig to use this area when he has to "go," and your life will be easier. If he has accidents during his training period, simply vacuum the carpets, or remove them to rinse, dry and return to the cage when clean.
Purchase several 4-inch or larger PVC pipes and elbows, and place them inside your pig's cage along with a few balls or toys. Make sure your guinea pig has something hard to chew on, since his teeth will continue to grow if he doesn't "file" them naturally.
If you have a cat or dog and want to keep your guinea pig from becoming lunch, you can create a lid for your cage using more of the cube grids, attached by wires or ties on one side and clipped together with a tension clip or wire in the front, for easy access.
This cage is designed to be kept on the floor where your guinea pig can't accidentally fall and hurt himself. If you have small children or other pets that may pose the threat of danger to your pig, you can build the cage on top of a table. Just be sure that you leave a lip or ledge all the way around the cage so that accidents are less likely.