Complex sentence: Given its postwar use by the military, all its runways, perimeter track and hardstands still exist but the World War II buildings have been removed, being replaced by modern buildings on the airfield, secured and guarded with fencing and other security devices.
Split into simpler sentences: Given its postwar use by the military, all its runways, perimeter track and hardstands still exist. Unfortunately the World War II buildings have been removed, being replaced by modern buildings on the airfield, secured and guarded with fencing and other security devices.