An informal garden planter made from a rigid plastic kiddie pool is very inexpensive and easy to make. It can be a great way to repurpose a family splash pool that is no longer being used by the kids. You can plant anything that has shallow roots, which includes most herbs and many vegetables as well as many annual flowers.
Any standard rigid (not inflatable) kiddie pool will work, but the bigger the better. Once filled with wet soil and plants, it will be quite heavy and difficult to move, so be sure to park it in the right place before filling. Don’t put in on the lawn unless you’re okay with killing the grass below. A large patio or gravel or dirt area may be best. Keep it off of wood decking because moisture trapped under the pool could damage the deck wood.
Raised planters have some special needs since the soil tends to get hotter and dryer from sun exposure around the walls of the planter. This may mean that you can plants seeds earlier in the spring than you would when planting an in-ground garden, but it also means you will need to watch moisture levels carefully. Raised planters typically need to be watered more often than do in-ground gardens.