I did not manage to guess what it is Mies, I am really intrigued!

Here is another one difficult to guess, based on an odd number, the 3 (the towers and the triangle of space on the top left)

Thanks for this exciting subject for the challenge, it is a very clever idea, and everyone has posted great entries. These challenges are very exciting and make me learn a lot watching the interesting ways to treat a topic that everyone shows, this is a great way of learning from others.