Compound on Park.

It is probably safe to assume that Santiago Calatrava is the only architect in New York who lives in a town house on Park Avenue. It is an even surer bet that Calatrava is the only architect who has what amounts to a compound of three town houses on Park Avenue. A few years ago, Calatrava, who designed the soaring train station planned for Ground Zero, decided to move his family from Zurich to New York. He purchased an 1885 Queen Anne-style town house with bay windows, one of a pair on the east side of the avenue between Sixty-ninth and Seventieth Streets, and among the few surviving private houses anywhere on Park. "We had stayed around there in hotels, and you get used to the neighborhood," he said, as if to explain why he didn't join the parade of architects downtown. "It is very pleasant. And I like the polarity between Lexington and Madison. One is for shoemakers and bread, the other is for fashion. It is all very nice."

After Calatrava redesigned the house from top to bottom and moved in with his wife, Robertina, the town house just to the north, a slightly grander building with a limestone facade, became available. It has an excellent pedigree--it was used for years by the philanthropist Paul Mellon as his New York office--and Calatrava decided to buy it and put his own office there. Then the mate to Calatrava's first house, just to the south, went on the market, and he figured he ought to buy that one, too. He is planning to turn it into living quarters for his three grown sons.

Calatrava just finished renovating his new office. It is sleek and white, without any of the swooping curves and anthropomorphic details for which his work is known. (Many of Calatrava's buildings are said to look like birds; he designed a skyscraper in Malmo, Sweden, that is called the Turning Torso.) The office looks more like the headquarters of a hedge fund than those of an architectural firm. There are white marble floors and black computers and conference rooms with glass tables and a huge video screen. The art--all made by Calatrava--ranges from a set of sculptures on pedestals in the main hall to a huge bas-relief in bright cobalt blue leaning against a wall.

Calatrava spends much of his time sketching and sculpting, and the shapes often turn up as buildings or bridges. He works in a large room on the third floor, facing Park Avenue. There is no ...