Hello everyone! I am new to the forum and I would like to ask about a question about a new kind of bicycle that I saw this weekend.

I'll do my best to explain it...this was basically a bike on top of a bike. there were two large wheels on the ground, and two smaller wheels on top of those wheels. I assume the rider had to pedal backwards to move forwards...but he was gone too fast for me to say for sure. it looked like a tall bike with extra wheels.

does anyone have any ideas as to what this was?? thanks!