With added purchases you can build the next buildings or use your imagination and design your own buildings. Even Einstein played with them.
I looked at the prices and, darn it, they are still too expensive for me, unless I close my eyes and not pay my taxes, get my septic tank looked after, my roof fixed and my car brought back to good running conditions. But there is no way I can bring myself to do that. The responsibility genes are too well developed in me. Could the superego just once disappear? I want to play. No chance.
For those who want to have a look at this play paradise and may be get any grand children you have hooked on them, here is the original German site. The site can be read in any language you desire. The second site is one of the US sites I found where you can buy the sets. I put "Anker Building block" in Google to come up with all kinds of links.
Go and play some.