New York City ? Empty space may seem impossible to find on an island crowded with people living in closet-sized apartments.

But Borough President Scott Stringer says even Manhattan has space to spread out, and up.

His office released an informal real estate survey, conducted by volunteers, showing at least 505 undeveloped lots and another 1,723 that appeared to be vacant.

That’s enough space to create nearly 24,000 housing units to meet New York’s future population growth, Stringer said.