I built this last year from around 5500 Lego pieces. It's a model of the furture European Extremely Large Telescope, to be erected n Chile during the coming decade. The model design was made by Dutch astronomer Frans Snik and you can read more about it and download the instructions and parts list here.
If you want to marvel at it up close, it is on display at the Astronomy Department of Uppsala University. They have one in Göttingen as well and I guess there are several more around.