A garage door whose technology sinks almost completely into the floor.

This garage door has the aforementioned advantage that only the Redstone lines to the triggers are above ground. The rest of the technology is underground. The garage door itself, however, must be made of material that follows gravity, e.g. sand.

Another picture from the inside:

Instructions:

Two times six pistons push the sand upwards. When they retract, it also falls down again:


Unfortunately, as I said, with most other materials, it can't be built because the pistons (even if they are sticky pistons) won't pull it down with them when they retract. 

If you work with levers, the redstoning is easier, but you can only operate the gate from one point (e.g. 2 levers: if one lever sends a signal, the other lever cannot change it). Therefore, the temporary redstone signal from a button must either trigger a permanent redstone signal, or disable it if it already exists. For this I used the following circuit: