The initial caverns of the Iron Way were discovered by the dwarven clans who settled the Dwarven Sea. The caverns were discovered when dwarves mined down beneath their settlements, and expeditions were mounted to map the extent of the caverns. Once overland trade was established among settlements, locations of caverns were shared and soon tunnelling teams embarked to dig tunnels to allow underground trade between settlements. Though many dwarves died in these tunneling expeditions, the success allowed for underground trade and transportation that was much safer than risking getting caught on the surface during the day.
The Iron Way is a subterrainian network of tunnels, passages, mines and caves that extends beneath the northeastern region of the Dwarven Sea.
Entrances exist beneath all settlements, linking them together by tunnels. There are also a number of entrances spread throughout the wilderness, though many are caved in or covered over by erosion. There are known entrances in Sea Hold, Irkalla, and Two Swords, and The Bore.
Below the manufactured tunnels of the Upper way is the Descent. Many parts of the Descent have iron spikes imbedded into the stone of the walls, effectively creating a ladder that gives the Iron Way it's name. Passages in The Descent can be large enough to allow flying monsters to prey upon food, or narrow enough limit the passage of humanoids. While most are vertical shafts that allow motion straight up or down, there are some places where the walls slope sideways or flatten out completely, allowing travelers a brief respite from climbing.
Reports from Peishan adventurers suggest that beneath The Descent there is an empire of ghouls that patrol the depths. Little is known by surface dwellers about the extent of this underground empire, but it's supposed to be quite large.
Undead of all types stalk the Iron Way. They are by far the greatest in number. If reports of The Ghoul Empire are to be believed, ghouls would be the next most populous, though scholars debate if ghouls are distinct from undead or a subtype. In the Upper Way, dwarves are most common, including Sea Dwarves, Azer, and Mountain Dwarves. Valkyrie and Burrowlings also live in communities that have entrances to the Iron Way. There is archaeological evidence of a race of people known as the Deep Geneen. Though there have been no reports of encounters with them in modern times, there is also know evidence of their downfall, so it remains unclear if they still exist.
The Iron Way is so vast and contains so many societies that there is no single overarching culture that is common to all peoples; indeed, it would be like asking what is the culture of the ocean. However, there are customs that are common to denizens of the Iron Way that cross societial lines. Tunnel design in the Upper Way varies depending on the people that dug them, but almost all tunnels built for travel are at least 10 feet tall. Flags are commonly used to mark boundaries between nations, and warn travelers when they will need to switch tracks.
The Upper Way connects the entrances to the surface communities via tunnels that contain mine tracks, magically enchanted to propel mine carts through the tunnels. The state of the tracks is unknown, and the network seems to be inaccessible for most adventurers.
The Descent has iron rungs imbedded in the walls of the caverns, and these assist in climbing.