Helvetinjärvi, Seitseminen Some hiking in Helvetinjärvi ("Lake of Hell") and Seitseminen national parks. Saturday route at Helvetinjärvi Entry to the park Map of Helvetinjärvi area A tree in the lake Cabin at Helvetinkolu Steep and narrow slot in the mountain leading down to the lake. Mire. Much more of these at Seitseminen. Sunday route at Seitseminen