Cave and Basin National Historic Site

Cave and Basin National Historic Site is a compact historic site built around Banff's natural cave and warm mineral springs. Inside, exhibits and short films tell the story; outside, boardwalks lead to the springs and wetlands. The cave itself is small and has a strong sulphur smell, so set expectations before you go. This isn't a bathing pool: the water is warm, and Banff Upper Hot Springs is the public place to soak.

The 0.4 km Upper Boardwalk takes about 15 minutes with little climbing. It passes the cave vent and the former hotel site, then reaches smaller springs and pools where pink bacteria, algae, fish and insects live. The 0.5 km Lower Boardwalk is about a 20-minute walk through more of the area's natural history, wetlands, fish and bird life.

For a longer wander, the 2.6 km Marsh Loop circles a wetland fed by hot springs. It's an easy walk of about an hour, though heavy horse use can leave it muddy after rain.

Rain and snow on Sulphur Mountain seep into cracks in the rock and travel about 3 km underground, where the water heats before rising back to the surface. Its temperature changes with how quickly it rises and how much cold groundwater mixes in. The rotten-egg smell comes from hydrogen sulphide produced by bacteria breaking down dissolved minerals.

These pools are more than a hot-spring curiosity. The endangered Banff Springs snail lives in only six spring groups, including Cave and Basin. The warm water also supports small fish, insects, algae and bacteria, so the basin is habitat to look at, not a place to bathe.

Cave and Basin has been a special place for Indigenous Peoples for more than 10,000 years. In fall 1883, Canadian Pacific Railway workers Frank McCabe and brothers Tom and William McCardell fenced the springs and built a log cabin by the cave. Their claim helped prompt protection of the springs and set Banff's national-park story in motion.

Parks Canada recommends 2–3 hours for the cave, exhibits, gift shop and surrounding boardwalks. If you only pop into the cave, the visit is much shorter; the walks and interpretation are what make a fuller stop. The site has parking, restrooms, a picnic area and a gift shop. Roam Route 4 serves the area, and the site is about 2 km, or a 30-minute walk, from downtown Banff.