A demilitarized zone, DMZ or DZ is an area in which treaties or agreements between nations, military powers or contending groups forbid military installations, activities or personnel. A DMZ often lies along an established frontier or boundary between two or more military powers or alliances. A DMZ may sometimes form a de facto international border—for example, the 38th parallel between North and South Korea. Other examples of demilitarized zones are a 120-mile (190 km) area between Iraq and Kuwait, Antarctica (preserved for scientific exploration and study) and outer space (space more than 100 miles (160 km) from the earth's surface).