Let the local skater boys have at it and charge a daily fee. Make sure the parents sign a waiver so they cannot sue you.. Buy a fountain liner and make it a big water fall with rocks and plants and ass some fish.

Townships in my area (Cape May County) offer free mulch. Call your local Municipal Utilities Authority and inquire of same - it comes from the live trees collected at Christmas and throughout the spring, summer and fall yard clean up. Wouldn’t hurt to ask. Then you can fill it and not spend so much on “free dirt” and start a new “in ground” garden…..

make a pond out of it unless it leaks in that case fill it