Achensee (Lake Achen) Often referred to as the “Fjord of the Alps,” Achensee is the largest lake in Tyrol. Surrounded by the Karwendel and Rofan mountains, it’s an adventurer’s paradise.

From its boulder-smashing Alpine rivers to its startlingly blue mountain lakes, Austria is ripe for adventures both on and under the water. Here are six of the best to try this summer. Though it ...