Anchor Stones are small stone architectural building blocks made from quartz sand, chalk, and linseed oil. They are sold sequentially in sets with an instruction booklet of plans for various constructions. This is a repository of additional constructions that can be made.
Building towers is one of the more satisfying constructions to make. Every now and then, you make one that actually looks like something. Here's a tower made with the Heinzelmannchen set. I think it looks like a lighthouse.