I have built one more shelf in my garage.

Lessons learned:

Building a shelf in a garage is easy – I have built a larger one before.
Building a nice shelf is a different story.
It is very labor-consuming.

(last time I was able to get away with “who cares” shelf as long as it is sturdy, because it is at a wall. This shelf, though, is in a the middle of my garage, so it got to be nicer)

The shelf is built from 3/4 maple plywood. I have rounded corners and routed it on the top and bottom.
The poles are from an old IKEA bed. The whole thing is sturdy enough for me to climb to the very top (yes, I tested it).

The most important thing is: being sloppy with measurements in the beginning will bite you later.

I cut 4′ x 4x into four 2′ x 2′. I whish I made them precisely 2′ x 2′, but I did not. In the end, I had to fit it to the column after it was assembled.

Also, drilling templates made out of a few pieces of wood glued together make projects like this much easier.

Also, the fastest way to glue two pieces of wood together is a high-temperature glue gun and vise. In a few seconds, it holds as good as super-glue (yes, I tried to hammer them apart).