The National Park Service has done an enormous service to us all by rejuvenating and preserving the historic hot springs bath houses and downtown of Hot Springs, Arkansas. Upgrading these health spa's has strengthened the local economy and preserved the health benefits and historical fabric for future generations.
Of course, historic preservation and reuse of existing buildings is one of the first and foremost ways to be sustainable primarily because it eliminates the need to produce all those new building materials, each of which comes with an environmental price tag. But this is probably just the tip of the sustainability iceberg as the Hot Springs Bath House District has demonstrated. Bath houses continue to attract many visitors providing local economic sustainability while preserving the local history, scale and community fabric. Both are enormous and continuous benefits to the local community as well as all of us seeking to soak and rejuvenate in the special hot waters that people have come from far and near to experience for more than a hundred years.
As more studies are done by NASA and others, these hot spring waters continue to provide new information on what makes them so special.