This is my third or fourth mob trap but the first one I've made a schematic of. Built up from elevation 6 to 128, there's 29 floors if I remember correctly. I took some ideas from a different trap I saw and modified it to my own liking. Uses flood gates to push monsters into the grinder that are timed by a minecart loop. I generally put two carts in the loop instead of one to have the mobs fall a bit faster but one can be used just fine.

I had some problems with mob spawn rates on the world I made this on so I stacked each floor with 3 spawners on each half. It mainly spawns creepers and skeletons and slimes (bottom two floors if they start jamming up the trap)

This trap features a drowning grinder and a mob-a-vator fed EXP trap which can easily be switched between by the flip of a switch. There are a few visual aspects that I haven't finished yet but I got interested in a different project once it was functional lol.

Note to any who may use: I used ice to speed along the mobs so place in a snow biome or a server that has ice melting turned off. And the second screenshot is actually covered with a roof but I removed it to show the layout of the floors.