From the National Park Service:
The Lunar Landing Research Facility is in the West Area of the Langley
Research Center. This facility was constructed in 1965 at a cost of
$3.5 million and was used by the Apollo astronauts as a training
simulator to study and practice piloting problems in the final phase
of the lunar landing mission.
The primary structure at the facility was apparently a 250-foot-high, 400-foot-long gantry with a hoist system which allowed researchers and test pilots to develop mechanisms and techniques for maneuvering mock lunar landers to a simulated lunar surface. Here's a scan of what the owner describes as a contemporaneous photo of the gantry and hoist, featuring one of several landers tested at the site.
The base of the Lunar Landing Facility was modeled with fill dirt to
resemble the surface of the Moon. Pock-marked holes, pits and craters
resemble the lunar landscape encountered by Apollo 11 when it landed
on the Moon in July 1969.
Here is a PDF of the Jan. 9, 1970 Langley Researcher newsletter where the site is discussed.
Here is a 2009 photo of the gantry taken by a Flickr user.
Here is a current aerial view of the gantry from Google Maps at N 37° 06.065 W 076° 23.344:
And the view from Google Street View (dated June 2016):