continent tier

The continent tier is the highest level of the region hierarchy. It holds the seven continents, and every other region descends from one of them.

The tier exists to anchor the hierarchy rather than to administer anything. No authority governs a continent, and its boundary follows geography and long-standing convention rather than a decision, which is why the count of seven is a convention and not a fact.

A country spanning two continents belongs to one of them here, because the hierarchy gives each region a single parent. The exception is recorded on the region, not by splitting the tier.