AstroWorld is worth a visit.

Baking hot - not all the lines (queues) had shade. Even the water rides which soak you to your skin do so in warm water. Don't miss the Dungeon drop - a vertical fall, feet dangling - but most of the roller coasters are fantastic too. Bring plenty of water to drink or buy a soda (fizzy drink) every half hour, and expect to find it an exhausting day.