The stone wall sits about nine feet below street level and perpendicular to the path of a planned subway tunnel and is too historically significant to cart off to a landfill. Archaeologists believe it was built at least 240 years ago.

But coming up with a plan for preserving the wall, discovered in November, presents a bigger puzzle. City officials must answer a string of questions: How much of the wall should be removed from the ground? How and where would it be displayed? Where would it be stored in the meantime? And who is going to pay for all of this?

Adrian Benepe, the city’s parks commissioner, said that he hoped some of those questions would be answered by the Metropolitan Transportation Authority.

But the planners will have to act fast. Joan C. Berkowitz, a partner in Jablonski Berkowitz Conservation Inc., said the transportation authority has asked her firm to take two weeks to document the current state of the wall in enough detail so that it can be taken apart and reconstructed.

Warrie Price, president of the Battery Conservancy, a nonprofit organization dedicated to maintaining Battery Park, said he hoped the wall could be reassembled and displayed to the public.