The Amur Line, following the Amur River, forms much of the border between Russia and China in the Far East. Established through treaties like the 1858 Treaty of Aigun, it has been a historically contested boundary, with the river serving as a natural divider.

The Administrative Boundary Line (ABL) separates Serbia and Kosovo, established after Kosovo’s declaration of independence in 2008. It remains a point of contention, with Serbia not fully recognizing Kosovo’s sovereignty.

The Antarctic Treaty establishes Antarctica as a region for peaceful scientific purposes, explicitly banning military activity, weapon testing, and mineral mining.

P-waves, or Primary waves, are longitudinal compression waves. They travel faster than other seismic waves and can move through solids, liquids, and gases.

China has the greatest elevation span, ranging from Mount Everest (8,848m) to the Ayding Lake (-154m), a difference of over 9,000 meters.

Angel Falls has the greatest single uninterrupted vertical drop of 807 meters.

The Maldives is the flattest country on Earth. Its highest natural point is only about 2.4 meters (approx 8 feet) above sea level.

Mawsynram, a village in the East Khasi Hills district of Meghalaya state in northeastern India, holds the record for the highest average annual rainfall.

Australia is the lowest and flattest continent, with an average elevation of only 330 meters. Note: Antarctica is the highest continent by average elevation.

On the surface of a sphere (like Earth), the shortest path between two points is an arc of a Great Circle, often used in aviation navigation.