Haavikkolehto - a protected site with many boulders left by the ice age - is also very interesting from caving perspective. Likely not everything here has been found. But the most spectacular cave is known from this Retkipaikka article.
I visited Haavikkolehto to draw a map of the cave. But I also realized there are more caves, e.g., right next to the main cave there are other boulders, and inside their cracks there are other relative long (maybe 10-20m) of passages in a single cave, though perhaps not as spectacular large opening as in the main cave. The above picture is from that second cave.
Cave map of the main cave, drawn by me, is here: