This mod will add a huge labyrinth that is almost impossible to get through, since there is no map that is always in sight to navigate by; instead, in different areas along the way in the labyrinth you can find maps hanging on the walls showing your current location, there are 4 such maps in total. including the starting one, if you come across one of them on your way, then you are on the right road.
Installation:
The modification does not require the game to be installed, just unpack the archive to any location and run the executable. More details about launching in the Readme file which is in the archive.