Is it an aeroplane? Is it an airplane?

The sign reads do not climb on airplane. This is perhaps the least scary sign here. Others say things like unauthorised people may be arrested and prosecuted.

What on earth is this place? It is RAF Alconbury, a British airbase playing host to the American airforce. It's basically an administrative and residential centre, as far as I can tell.

It's a bit disconcerting to see a tall barbed wire fence keeping people out with playground equipment just inside.