Hidden behind weeds and broken bricks, amid the hum of traffic from the nearby Brooklyn-Queens Expressway, lie 20 acres of abandoned grassy hills, crumbling Greek Revival mansions and Second Empire structures that few New Yorkers have ever seen.

There is the home of Dr. E. R. Squibb, who built the first still for making pure anesthetic ether, and a grand naval hospital with antebellum staircases and soaring windows, where Confederate soldiers were reportedly imprisoned during the Civil War. There is a tennis court, barely visible through vines, with a sign warning users to wear proper attire, and a laboratory, an officers’ club and even a morgue.

After decades of neglect, this hidden corner of the 300-acre Brooklyn Navy Yard, known as the Naval Annex Historic Campus, may be ready for a long overdue makeover.