What's the biggest thing a 3D printer can print?

I really wanna 3D print some large fractals (anywhere from 3ft to 6ft tall/wide/long. I know it might be on the more expensive side, but Google's not being so definitive on what and all it can print. I know when it comes to what I have in mind--a giant Menger Sponge--all I'd have to do is print several smaller iterations, and then glue twenty of them to form a larger iteration, as many times as I need to. But theoretically... how big can they print?