Tunnel of Ancestors

Originally started immediately before the Cataclysm as a southern exit route from the Nocthian Caldera, this ~20 mile tunnel and cavern route through the southern wall of the Caldera down into the Byssian Highlands was only completed due to the urgent need of the Nocthians to flee the automaton forces of the Deep Mind about 50 AC. It was then sealed up with strategic deadfalls and cave-ins for another 150 years, until in 215 AC it was re-opened after the fall of the Hungering Frost.

Winding its way up through the volcanic lava tubes, caverns, and artificial tunnels that pierce the mountains, it is a masterpiece of late-age arcane and primal engineering, but is still quite risky for caravans, due to instability and the steep traverse (as it rises nearly 8,000 ft over its run). In recent years, as thawing relations with Wyrmhold have granted access to mechanical engineering and technology, golem-operated lifts have been installed in some places, dramatically easing passage.

At the top lies the city of New Nocthia; the bottom opens up still high in the mountains of the Highland, leaving another 60 miles to the Home of the Elements, the nearest publicly-available settlement (as sparse as its comforts are).