This road spans the continent, connecting the Eastern and Western kingdoms. The full length is 2700 miles, and takes the typical traveler about 5 months to traverse. (4 for dwarven caravans, 6 for unoptimized caravans) The kingdoms share the cost of maintaining it and the fast messenger system – with a system of checkpoints and fast horses, royal couriers can travel the route in just 2 weeks.
The road itself dates back over 1400 years, but it was paved by a combination of elven wizards and dwarven engineers starting about 300 years ago and finishing just 6 years ago. This expansion greatly facilitated trade and travel between the kingdoms, and the road is meticulously maintained. Intentionally damaging or blocking it is a capital offense. Banditry is somewhat common, but punished brutally when perpetrators are caught. People travel in caravans for speed and safety. There is only about a 10-week window where caravans can leave from each end of the road, although of course not everyone travels its whole length, those weeks are the busiest of the year.
In the east, a treaty of the five major powers created the Free City of Dunduraltea. The name is somewhat misleading, as it has no self-governance and is heavily regulated by a complex web of treaties and agreements. It is carved out of dwarven lands, and serves as a place where caravans can form and set off without being taxed or otherwise restrained. There is a small permanent population, entirely based on service industries - no farm larger than a kitchen garden is permitted, shops have a strict list of goods that are allowed to be bought and sold (no luxuries, no trade goods, limited quantites per buyer, all transactions must be in coin or kingdom script, no trades allowed), and the city is governed by a rotating cast of functionaries from the four current kingdoms. Inns and taverns do very well here, and something can be found for everyone, from raucus party bars to quiet luxury accomodations.
The western terminus is the city of Altonamara, in the elven kingdom. Permits must be obtained for trade caravans to pass through freely, and typically require a sponsor in the final destination. The major trading companies are willing to handle this paperwork for independent players in exchange for a small percentage, but it’s possible for an individual to go it alone if they are well-versed in trade laws and patient enough to wade through the elven bureaucracy. Paperwork for people is much easier to obtain as long as they aren’t wanted by the law, and most people find the forms easy enough to handle alone.