Gate
Level of lava flooding ~~~ /████\
provides a simple protection here, if you don't have magma safe items for your gate at least.
The drawbridge essentially doubles as a gate, and as I learned earlier, raised bridges behave like solid walls when it comes to lava, so they are magma-proof no matter what they're made of.
But, sure, I could just raise the whole fort one z-level, that would provide some protection from the flooding, but then the line-of-sight would be lost. I plan on building siege engines on the ground floor of the towers to pick off bigger beasts or waves of enemies on the other side of the moat, and those need a straight line-of-sight to the enemy, so if I raise the walls, those will no longer function.
Well, it seems like covering the fortifications is not an option just yet. I
can cover the ones on the ground floor with 10 wide and 1 long bridges, but somehow it seems there is no way of magma-proofing the upper levels... Well, I still hope someone has an idea...
in order for pumps to be fast (as was illustrated with the reservoir many Z-levels above the pump) the pump will not be safe for a pumper, only for powered pumping... well, you could make a short U bend since magma won't rise up a hole without a pump behind it...
So you are saying, that without a pump, the magma would never reach the second floor?