The three-fan array comes out in one piece. It's held in place with six screws and connects to the logic board with spring contacts—no fussy cables to deal with!

The three tower fans pull cool air through the cheese-grater holes at the front, and push it across the logic board through the various heat sinks. Then the blower fan vacuums up the hot air and spits it out the back.

A few interesting things about this arrangement:

Most tower computers have dedicated fans for the CPU and GPU in addition to fans at the front & rear of the case. The Mac Pro just has front and rear fans, which supposedly provide enough cooling to keep it chill under stress.

Another thing most tower computers have: some sort of debris filter to get rid of particles in the air that the cooling fans pull in. Apple's engineers are on record saying they don't need that, but only time will tell how dusty these things get.