This is an early clock design based on a minecart pulse-generator and a small divide-by-4 section to send signals to 4 piston-based clocks (one on each side of the tower).

You may place it in your map, or use the basic concept for creating your own clock tower. See images for a more in-depth view of the compact piston-based memory cells.

Have fun and go build something big!

Additional Notes

MCEdit was not used in the creation of this clock tower. Sometimes the circuitry bugs due to too many torch-inverters being stacked. Additionally, the sand in the piston memory cells sometimes disappears on beta servers. To repair both mistakes, place new sand and replace one redstone torch.