Right in the middle of Tammisaari there's a classic "stone table", Ramunderinkiven onkalo (The Hole of the Ramunder's stone). Stone tables are stone formations where a rock sits on other stones. Ramunder is the strong man of old tales, and the story is that he threw a large boulder to crush some giants, giants that are now the stones holding up the boulder.
There's also an old story about Carl Sköld, a villain that hid his treasures under the stone.
But these are old stories, I happened to run into some inexplicable conspiracy theories on the Internets about how it must have been some ancient civilisations that set up these stones, and that the arrangement is set to depict broody hens caring for their eggs.
Back in reality, stone tables are boulders that happen to have landed on top of other rocks after glaciers, earthquakes, collapsed cliffs, etc. moved them.
The stone is listed in the Raasepori sightseeing page, as well as in the book Suomen Luolat (Finnish Caves).
I also draw a rough sketch for a map of the "cave", here.
See more caving stories at Planetcaver.net, and all Planetskier and Planetcaver stories at Blogspot and TGR! See also my cave map that runs the Psgeo software that has now been open sourced! This article and photos are (c) 2020 by Jari Arkko. All rights reserved.