The largest hot spring pool in the nation is at Glenwood springs. 

Glenwood Springs

In the middle of the woods there are a few hot spring pools. The location makes it one of Colorado's favorite. After dark clothes are optional. 

Strawberry Springs

There are a few resorts right in town and on the river. 

Pagosa Springs

Sitting below a 14er, this resort has a few pools right on the side of the river. 

Mount Princeton Springs

Nestled in a little valley , this town has a few hot spring options. 

Ouray