The Apollo 13 Aquarius lunar lander model, which you can download and print on 21 sheets of A4 paper.

The first few sheets of the model are lined up and glued together to provide the basic shape of the upper ascent stage. This is the part of the craft that astronauts would ride back up to the orbiting command module to hitch a ride home. Well, that’s how it was supposed to work. Apollo 13 famously never made it to the Moon. Then you get all the external details for the ascent stage, support legs for the descent stage, and finally the engines.

Just looking at the model above, you wouldn’t think it’s made of paper. This isn’t origami, so the distinctive folds that can give away a material as paper aren’t there. Many of the cut outs are rolled into tubes to form supports and lander legs, and others become little boxes that house components on the lander’s surface. It even includes a removable wall section to reveal the detail inside. Yes, there are sections of the design you fold up to create hoses, instrument panels, and other objects that you’d never see without opening it up.

There are instructions to help you assemble it, but the site is in Japanese. Google Translate seems to understand pretty well, though. Each of the 21 pages is a big PDF between 20 and 30MB (download links down near the bottom). There’s a lot of detail, so you need a good printer to print everything well.