Old Airfield
From Kerbal Space Program Wiki
The Insular Kerbal Space Center is a landing strip, hanger and, command center located on the largest of the string of islands east of the main Kerbal Space Center. The landing strip has a grass-like texture which makes it harder to find from the air. It is also quite elevated making it hazardous to overshoot and falling off the strip or turning at an end.
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Spoiler: Easter egg