For this project I built a 10 foot tall Lego Tower. The Tower was built with the widest section at the bottom and the thinnest section at the top, ending in an antenna. The widest section is an 8 by 8 square, and it decreases to a 6 x 6, then 4 x 4, then 2 x 2 and finally 1 x 1 square.
I made the tower over a series of weeks and it was a lot of fun. One issue I ran into was that I started running out of bricks which were not 1 x 1 or oddly shaped, so I bought some Lego equivalent blocks on Amazon. The best deal I could find was 1,000 blocks for $17. This set is really good, as the vast majority of the bricks are 2 x 2 or larger. Other sets of blocks advertise having a lot of blocks (1,000 or more) but most of the bricks are 1 x 1 so they are not that useful for building. The set I found can be found on Amazon here:
Here is a video describing the Tower in more detail: