You don't have to live next to the ocean to live in a lighthouse structure. If I had it all to do over, I would seriously think about a three-story cylinder. MANHATTAN is a vertical city, but it is largely experienced horizontally. Most Manhattanites live in apartments, with rooms spread out laterally over one or - if they're extremely lucky - two planes. The real vertical dwellers are those who live, paradoxically, in a pre-skyscraper New York. These are the town-house dwellers - in particular, the skinny town-house dwellers (skinny referring to houses) - those like Kathy Landau, Michael Kantor and their three children, Emma, Sacha and Twyla, who live their lives in layers. Their 12Â½-foot-wide, five-story Queen Anne-ish brick town house on East 30th Street was built in 1880 by a man rich in daughters - he had two - but not so rich in cash. He followed a practice common to many builders at the time, which was to squeeze two houses - in his case, one for each daughter - on a 25-foot-wide lot. Twelve and a half feet may seem mingy, but it does net 12-foot-wide rooms - a perfectly decent size - in this case arrayed two to a floor and stacked on three levels beginning on the second floor. (The first floor is a studio apartment, rented out to help defray mortgage costs; the basement is an office/playroom.) "It's living in a vertical six," Ms. Landau said. "It's about moving up and down a lot, and being judicious about what we put where."