The Narcisse Snake Pits are located in the Rural Municipality of Armstrong about six kilometers north of Narcisse, Manitoba, Canada. The dens are the winter home of tens of thousands of red-sided garter snakes (Thamnophis sirtalis parietalis). These pits are the largest concentration in the world of this particular type of snake. Their winter dens are subterranean caverns formed by the area's water-worn limestone bedrock. In the spring, they come up from their dens to the snake pits, where they engage in mating rituals.