Lake Mastis is the reason Telšiai opens up instead of feeling like a tight inland town. The promenade along the northern shore is simple but pleasant, with water views, sculpture, and enough space to slow down after the museum and cathedral.
It is best late in the day, when locals come out for walks and the light sits low over the lake. Do not expect a wild nature escape; this is a town lakefront, and that is part of its charm.