The Misty Lake (霧の湖, Kiri no Mizūmi) is a large lake located at the foot of the Youkai Mountain. It surrounds a small island which hosts the Scarlet Devil Mansion. It seems to be a home to Cirno and other fairies, such as Daiyousei.
The river streaming into the lake is from the Youkai Mountain, and the mist around it makes it difficult to see through at noon. In the games, it was rather common to see up until Mountain of Faith, and was absent for 4 games, untilTouhou Hisoutensoku was released. Embodiment of Scarlet Devil's Stage 2, some of Phantasmagoria of Flower View's Stages 1 and 2, and the whole Level 2 of Shoot the Bullet took place somewhere within the lake's area. In Touhou Hisoutensoku, Sanae's and Cirno's Stage 1 took place right by the lake edge.