Enter a captionQamdo Airport was the highest airport in the world by 4,334 m (14,219 ft) above from sea level. (IATA: BPX, ICAO: ZUBD), also known as Changdu Bangda Airport, (Tibet, China)
information by http://www.gcmap.com/airport/BPX
map image via skybrary.aero
Then Daocheng Yading Airport came had the record with 4,411 m (14,472 ft) high on 16 September 2013.
Really long runways. Why?
Location height causes reduction in engine and lift performance. So aircrafts need more than normal lift-off speeds and so longer runs.