In the far east of Finland, where the land loosens into water and forest in equal measure, Lake Saimaa spreads out like a shattered mirror. It is vast, quiet and intricate, a labyrinth of inlets and islands that seems to have been sketched by ice and then softened by time. More than 13,700 islands rise from its surface. Pines crowd the shorelines. Mist hangs low in the mornings, turning the water silver before the sun lifts it away. This is the largest lake in Finland, and one of those places that feels less like a destination and more…