You conjure a large rocky pool, 20 feet in diameter, at a location within range.  The pool is fed through a connection to the Plane of Elemental Water, and is filled with fresh, steaming water.  The pool is large enough to comfortably fit up to 8 Medium-sized humanoids.  Along with the pool you also conjure enough food and fresh drinking water to fulfill the daily requirements of your guests.  The pool remains in place for the spell's duration.  At the end of the hour, the rocks that surround the pool crumble to dust,and the water evaporates into a large puff of steam that instantly dissipates.  Any remaining food or drink provided by the spell also disappears when the spell ends.

A creature taking a short rest can spend an hour soaking in the sauna's waters and eating the food that it provides.  At the end of the hour, when the sauna disappears, any creature that rested in this way for the spell's full duration gains the benefits of a long rest, instead of a short one.  Once the sauna disappears, it cannot be conjured again for 24 hours.  Attempting to summon the pool again before this time elapses expends the spell slot, but fails to conjure the sauna.