Mountains
Conundrum Hot Springs is a long hike that needs a permit and a bear canister
Conundrum Hot Springs is a set of natural hot pools high in the Maroon Bells-Snowmass Wilderness, reached by a long trail up Conundrum Creek south of Aspen. It is a beautiful trip, but it is not a quick soak. The hike is many miles each way and gains a lot of elevation, so most people backpack in and camp overnight.
Camping overnight here requires an advance permit. The Forest Service uses a reservation system for the busiest parts of this wilderness, including Conundrum Hot Springs, and you reserve a specific campsite for your group. Each site has its own group-size limit, so the number of people you can bring depends on the site you booked.
Two more rules matter. A bear canister is required for backpackers in this wilderness, to keep food away from bears and bears away from people. The trail is usually clear of snow for a summer-to-early-fall stretch; outside that window the route and trailhead can be snowed in and hard to reach.
Permit release dates, group sizes, and conditions change each year. Check the White River National Forest pages for the Conundrum Creek Trailhead and the Maroon Bells-Snowmass Wilderness before you plan a trip.
Sources
Official or primary sources used for this note. Local details can change, so confirm before acting.