An Apartment Off Park Avenue With a 50-Foot Skybridge

An apartment built around a 50-foot-long skybridge, which links two buildings on East 77th and East 78th Streets, is so strange that its current owner wondered if it was a one-off. So he put an ad on Craigslist to hire someone who could “walk river to river,” as he told the Daily News in 2007, “and look for any other bridge that connects someone’s private residence” or “ask people walking dogs if they knew of anything like this.” (The answer: there’s at least one other apartment built…