Waypoints are landmarks that maintain a connection to the Otherworld regardless of boundary locations. To use the analogy of water receding from the land, waypoints are puddles that have been left behind as the water levels fall. Depending on the waypoint, these connections may remain indefinitely or simply fade more slowly than typical for the area. Waypoints can be divided into living organisms and ritual structures.
The first order of waypoints, that of living organisms, are things like trees and fungal colonies that live on both sides of the reality divide. If the version of that organism is removed in our reality, ie. a particular tree is cut down, the connection is removed and the waypoint ceases to be. As a general rule, organisms that provide this sort of connection are ancient – as with the connection between ancient woodlands and the Otherworld in general – but certain species such as yew and certain colonies such as rings of mushrooms or toadstools should be viewed with caution.
The second case, that of ritual structures, seems to particularly cling to stone rings, circular earthworks and old burial grounds. Christian sites of worship may also be waypoints, particularly if they were converted from earlier ritual sites. However, if the site is close to modern developments, they are unlikely to remain waypoints and the strength of their connection fades with lack of ritual. Scientific studies into what makes ritual so important have yet to be undertaken. The most famous example, of course, is Stonehenge.