The tour was wonderful! Our driver was comical and friendly, and knew a lot about Houston and the city's history, really interesting! Loved the space centre too! We want to come back to Houston for a longer stay to discover more :
I booked the tour mainly for the Space Center but I really enjoyed the 90 min tour of the city as well.
I had some trouble finding the location of the visitors center, but it's located at 1302 Dallas street.
Warning: The tour took 7 hours, not 6. We started at 10 am and were back at the visitors center 5:10 pm.
There was a good amount of time at the Space Centre - not enough to see everything, but 4 hours was probably close to saturation point. The downtown tour was also interesting. The group was small - about 6-8 people.