Michael Stern is the founder and chief executive officer of JDS Development Group, a development, construction and acquisition firm working in New York City and Miami. He builds on ground that resists being built on: a supertall in the courtyard of a landmark, a tower rising out of a designated banking hall, twin residential towers joined in the air by a skybridge. The work turns on air rights, site assemblage, preservation review and the structural engineering that lets a slender building stand. He writes about how those constraints get solved.