Threshold exists in the space between two countries that no longer meaningfully exist, and it has turned that ambiguity into a national identity. Built on Lake Huron's central ridge — roughly equidistant from the former Michigan and Ontario shorelines — Threshold occupies water that both the remnant Canadian federal government and GLMZ's Corridor Council claim jurisdiction over and neither can effectively enforce. The city was founded in 2171 by a mixed Canadian-American group who recognized that the sovereignty confusion created a permanent legal vacuum. They dropped their first accretion framework into water that was simultaneously Canadian, American, and neither, and started growing.

Threshold's seacrete is pale grey, built from Huron's lighter mineral profile — cleaner water, less iron than Superior, more calcium carbonate. The resulting structures have an almost marble-like quality, smooth-surfaced and bright compared to Deepwell's volcanic darkness or Freestone's rough organic textures. The city sprawls horizontally rather than vertically, its platforms connected by arched walkways and canal channels that give it the appearance of a floating Venice built from living stone. This horizontal spread is strategic: Threshold covers more surface area than any other lake city, making it harder to blockade and giving its defense forces — the Borderwatch — multiple angles of engagement.

The sovereignty dispute is Threshold's defining feature and its greatest asset. Both Canada and GLMZ claim the city is in their waters. Neither can act on the claim without provoking the other. Threshold exploits this deadlock ruthlessly, maintaining diplomatic relations with both sides while acknowledging neither's authority. The city has become the de facto neutral ground of the Great Lakes — a place where shore-based factions can meet, negotiate, and trade without either side having jurisdictional advantage. Diplomats, fixers, intelligence operatives, and criminals all use Threshold as a meeting point. The city charges handsomely for this neutrality, and the revenue funds an infrastructure that's more refined than any other lake city's.

Governance is bicameral — a nod to the city's dual-heritage founding. The Shore Council handles external relations and trade, while the Reef Council manages internal infrastructure and civil affairs. Elections are annual, contested, and occasionally theatrical. Threshold's culture is cosmopolitan in a way that Deepwell's mining solidarity and Freestone's anarchist idealism are not — this is a trading city, a diplomat's city, a city that understands that its survival depends on being useful to everyone and loyal to no one. Population: 185,000, most of them bilingual in English and French, and all of them fluent in the language of strategic ambiguity.