The three Lahti ski jumps — the smallest is around 60 metres, the largest 116 metres — rise straight out of the centre of town and are visible from almost everywhere in Lahti. They were built (and rebuilt) for the Nordic World Ski Championships in 1926, 1958, 1978, 1989, 2001 and 2017, and they are still the venue for the FIS Nordic World Cup ski jumping events held each March.
You can take a lift to the top of the largest jump, and the view from there over Lahti and the lakes is reason enough to go even in the off season. The summer swimming pool at the base is a happy quirk of the site.