I have long been perplexed by this artificial-looking hill north of 19th Avenue in eastern Astoria, just west of the Rikers Island Bridge. It's the fairly large (15 acres or so) treed area visible here, and you can see its topography, quite striking in this otherwise flat area, here.
It's owned by the Port Authority, according to numerous "No Trespassing" signs posted on the fence that surrounds it. Much of LaGuardia Airport, operated by the Port Authority and sitting just across Bowery Bay, was constructed on landfill from Rikers Island; maybe this was an intermediate site where dirt was stored after being transported from Rikers. Or perhaps this was once a landfill itself — this map makes it look like that may be the case.
The possibilities are many, but possibilities don't pay the bills. Or something like that. For the time being, the true origin of this little mountain remains shrouded in a mist of maybes.
UPDATE: The this-was-a-landfill hypothesis has taken the lead! (See comments below.)
UPDATE: I received an email from a current Port Authority employee saying that this hill is known internally as Ingram's Mountain, and that it was supposedly created from the rock excavated during the construction of the Lincoln Tunnel's third tube.