Boulder Hot Springs Inn and Spa

Between Helena and Butte in the Boulder Valley, this historic inn sells day visitors the whole place for one price: an outdoor pool at 96-100 degrees, indoor plunges at 103-106, steam rooms and dressing rooms. It runs as an alcohol, drug and smoke-free property, so leave the cooler in the car. You'll shower before you get in, there's no lifeguard, and kids under 12 need an adult with them. Day use runs 10am to 8pm every day. Come on a weekday and adults pay $12 rather than $14, and if you'll be back, the 10-pass costs the price of 9.