The Canadian National Park system was effectively born at these hot springs, discovered accidentally by three Canadian Pacific Railway employees on their day off in 1883 (though known to indigenous peoples for 10,000 years). The springs quickly spurred a flurry of private businesses offering facilities for bathers to enjoy the then-trendy thermal treatments. To avert an environmental catastrophe, the government stepped in, declaring Banff Canada's first national park in order to preserve the springs.
There's no swimming here anymore, but the site reopened as an impressive museum in May 2013 after a two-year restoration. Visitors can see the original cave, then stroll out onto a terrace that covers the former lower mineral springs pool. From here, a boardwalk with interpretive signage leads uphill to additional springs and the cave's upper vent.
Signposted just behind the complex are two more walking trails: the 2.3km Marsh Loop Trail across the park's only natural river marsh, and the Sundance Canyon Trail, leading along the Bow River to a beautiful side canyon.