Stairway to heaven
The alpha zombie on this map has no shields and 300% damage resistance and it has grenades.
all zombies have 75% gravity.
regular zombies have shields with 100% damage resistance...
Humans spawn with nothing but a magnum.
This is how I made it fair for the zombies.

This is where the zombies spawn.

This is where the humans spawn.

This antennae doesn't spawn for 45 seconds... so the humans have to fight off the alpha zombie while waiting for it to spawn...

\
Teleporter to the next part

This is where you come out.

This is probably the hardest part to make.

This part is pretty hard to make too.

here's what it looks like once you finally make it...

This is just a small extra building I put in for people who can't make it to the top...

View from the inside.

Here is a picture of me making the hardest jump
Link to the map:
Halo 3 File Details
Link to the game:
Halo 3 File Details