The odd-shaped block at Canal and Varick Streets is, in some ways, an architect’s dream. Even the nearby Holland Tunnel entrance, nominally a downside, ensures that whatever goes up there will be visible on all sides. The owner, Trinity Real Estate, cleared the site earlier this year, and says it’ll be used as a sculpture park until plans firm up. (There’s already a small plaza next door, Juan Pablo Duarte Square, with a statue of the Dominican hero.) New York asked four architects to come up with ideas for the plot (which, we will admit, faces our offices). We required only that the result include a residential component and that it more or less meet zoning requirements.