Canadian Rockies

Medicine Lake is a geologic anomaly in the sense that it is not actually a lake but rather an area in which the Maligne River (flowing from Maligne Lake into the Athabasca River) backs up and suddenly disappears underground.
Canon EOS 5D Mark IV, EF24-105mm f/4L IS II USM, 45 mm, ISO 1250, 1/1250 sec at f / 16, © 2017, David W. Boston