Minecraft wiki entry for Traps, associated text: If you want to protect the landscape, you can place 2 water sources at the bottom of the hole. Place a half slab at the bottom as sand/ gravel may quench the water source. This method will reduce the dealt damage, however.
This is well disguised next to a door; the player may think it is to open the door.
By digging a pit underneath it, the player might fall into it.
Try to camouflage the landmine by making it less noticeable, e.g. grow tall grass around it.
Concrete powder cannot be used in this design, the concrete powder will harden into concrete upon contacting water and quench the water source.