Murder Holes

Murder Holes is an important technology in Age of Empires II that is researched from the University in the Castle Age.

Effects
Murder Holes is important as it makes defensive structures such as the Castle, and Guard Tower (and it's Feudal Age and Imperial Age counterparts) have no minimum range. This means that they can attack infantry and other units that are attacking the base of the building, which is something that is not possible without this technology. This technology then effectively removes these structures' biggest weakness.