This is my entry for the 4th round, a very detailed defensive tower with several elements such as: a improvised stable, a crossbow in the upper part, a habitable floor, etc. The number of pieces is 2991 and it has a modular system so each floor can be built separately. It can even be extended from the 3rd floor. Very easy to build and many possibilities. I hope you like it and if you want to support it (Voting and commenting your feedbacks) -> click on the link below.
https://www.bricklink.com/v3/designer-program/series-4/1379/Ballista-Tower