The Houston Marathon is an amazing race. It is very well organized, and went off without a hitch. At the start, both marathoners and half marathoners start together and run the first 8 miles together... that part of the race is pretty crowded. After mile 8 it thins out. The course if mostly flat there are some hills for the over/underpasses. The aid stations and volunteers are phenomenal. There is a ton of crowd support by very enthusiastic spectators.