Lakes in Switzerland: refreshing turquoise mountain lakes. Visit one of the beautiful mountain lakes in Graubünden, where families especially are sure to have a great pool experience. In Graubünden there are 615 mountain lakes. Some are filled from glaciers and stay cold throughout the summer. Many other mountain lakes in Switzerland are warmed up by the sun in the summer, so there's nothing stopping you from taking a refreshing dip in a lake.