When an Irish developer stepped in to buy a large plot of land in Chicago recently, it started a whirlwind of rumors as to whether the developer intended to use the land to build something other than the 2000-foot Santiago Calatrava-designed skyscraper that had long been intended for the spot. The developer is reassuring the city that he plans to begin negotiations with Calatrava shortly on what would be the world’s tallest tower. Some skeptics “contend that the $1.2 billion project is economically unfeasible.”