Botanic Research Institute of Texas (there is no charge for a tour around the facility). The building was constructed with reclaimed supplies from the public health building that was originally on the site. Other building materials were carefully considered which resulted in bamboo ceilings and wool carpets (rapidly renewable materials). The foyer wall is cypress wood made from logs that sank to the bottom of a river as they were being transported to market over 100 years ago. The side of the building faces north and has the most windows and little direct sunlight while the southern wall has smaller, slit windows and walls of thicker construction.
The Institute is home to over a million plant samples that are frozen to destroy fungi and insects and then sorted and cataloged before storage in movable cabinets.
Even the roof of the institute is used as a research project, featuring plants that may have been part of the original Texas prairie. You can see pictures of the living roof here.
There are also many programs for children.