Hole is an Adventure Map feature that can be located on any land tile - that is: not water. They can either be placed on the map by the map-maker, or they appear after a hero has dug the ground. Digging has two purposes. Firstly, it is typically the only way to find the grail artifact (another possibility is to find a fired hero with the grail artifact in a tavern). Secondly, tiles with holes cannot be disembarked with a boat. This makes digging holes on the shoreline in order to prevent enemy heroes' invasions a strategic feature.