Cairnroads

All cairnroads lead to kelp.

The shallows of Sphaera's central and southern ocean are criss-crossed by a network of peculiar stone structures. These are the cairnroads, low cobblestone walls that run for hundreds to thousands of miles along the seabed, marking the safest and most direct routes between marine settlements and trade centers. Visible from the surface in most shallow waters, the cairnroads are used by all seafaring species as guides during voyages. The cairnroads are built and maintained by the umibōzu, and as such have a bias towards umibōzu-accessible locations. Most smaller offshoot cairnroads terminate at umibōzu plantations and umibōzu-kawataro trade sites at river estuaries, though the larger and more prominent walls typically lead to major multispecies maritime settlements and ports.