We did the Discover Houston tunnel system tour and had a great time. We toured the vast air conditioned tunnel system under the city, and ate lunch while we were down there, plus we went to the observation deck of the Chase tower, went to the visitors center and toured some of the other great buildings in downtown. Our guide, Sandra, was amazing and we really loved her. She is DEFINITELY an expert! We were the only native Houstonians on the tour, but that's fine. I take pride in being a Houstonian that explores all my city has to offer!