One thing I regret is that I took the tour on my second day I stayed. Take it first after you check in to your hotel. Why? Because, it shows you every place you want to go, afterward. This tour has a 75-minute tour of downtown Houston. You can see and locate all downtown Houston's attractions. You can spawn off several mini-tours on free bus routes. If it is too hot, go underground during the week in the Tunnel. Then, they take you to the Space Center in which you see suburban Houston. It is an outside bus, and you can't bring your umbrella. It is pricy, but for 1 or 2-day stay, you can't beat it.