What do you mean, when you enter the central square for the first time you find in the middle a rock.
On that rock you see the tower, you have to bring down the rock then you can enter the tower.
You can find a text walkthrough with lots of screenshots on : www.pcgameswalkthroughs.nl.
You have to use google translate because it's in Dutch.
Later on in the game when the rock is down and you can enter the tower, then you have to bring the tower further down and you go underground.
Playing on windows 10 was no problem, I played it in 2016 and wrote the walkthrough in 2017.
Let me know what you mean with raise the tower up.