Crater of Diamonds State Park is a really unique park near Murfreesboro, Arkansas where you can actually go and mine your own diamonds. Well, if you have luck at least! In fact, the Crater of Diamonds State Park was where both the largest diamond in US history and the only flawless diamond in US history were found. These days, there are plenty of diamonds still to be found and the park regularly sends out news releases with big finds. Actually, something like 30,000 diamonds have been found since the park opened.
If you get a bit sweaty digging for diamonds, there's also a water-park in summer where you and the kids can go and cool down. Entrance to the water park is only around $5 and there are several different pools, water guns, castles, slides and the like to play on. Like I said, it's one of the most fun and unique parks in the US and hey, you just might strike it rich!