Living in a landmark building like Colonnade Row may sound romantic – after all, the residences, built in 1833, once housed Cornelius Vanderbilt, Washington Irving, and William Makepeace Thackeray. But that imposing Neoclassical façade hid an elegant mess. When architects Clarissa Richardson and Heidar Sadeki, of UT, were called to renovate this duplex, they found floors that canted right like the deck of a ship, French doors that were crumbling to dust. Even the marble fireplace was falling apart. UT held on to the mantelpiece as a totem of the building’s grand past, but stripped the rest to its bones, creating a smooth, streamlined space. They kept the bedroom small and gave the bathroom – fitted with two oversize lilac tubs – a glass wall, to integrate it into the living space (yes, the glass turns opaque). The other design challenge was accommodating the owners’ two diminutive and obsessively loved dogs. Wherever possible, the architects kept things soft and grounded – low sofas, leather steps, rubberized stair treads. They’ve designed for man’s best friend, without compromising their luxurious, ultramodern version of Zen. That’s an idea that works in any era.Left and above: Colonnade Row is landmarked, so even the simplest gray wooden window boxes had to be approved by the Landmark Commission.