Finlandia Marathon is an annual running event and it reaches over 2 000 participants every year. The route of the marathon follows the shores of lake, which is situated just beside the city. Participants can choose between the whole marathon (42 km), halfmarathon (21 km) or "Valon Kymppi - " (10 km).
There are also othes shorter races included in the event.
More info: http://www.finlandiamarathon.fi/