The Extell Development Company, which is headed by Gary Burnett, has commissioned Steven Holl to design a major, mixed-use tower at 366 Tenth Avenue at the northern terminus of the High Line Park at 31st Street.

Mr. Holl showed a rendering of the planned tower last night on the Charlie Rose television program and said it would contain about 200,000 square feet of residential space, about 400 hotel rooms and art gallery and retail spaces.

The rendering seemed to indicate that it would be more than 50 stories tall and that it would rise in three major setbacks and that the silhouette of the slender tower would somewhat resemble an elongated, angled "S."

Mr. Holl said he had been worked on the project for about 18 months but contracts had only just been signed.

Mr. Holl is famous for his collaboration with Perry Dean Rogers Partners Architects on the very impressive design of the Simmons Hall student residence building at the Massachusetts Institute of Technology. That project is distinguished by its 18-inch deep windows and cut-out forms.

Mr. Holl has also won widespread praise for his recent major, luminous expansion of the Nelson-Atkins Art Museum in Kansas City, Missouri and a huge residential complex nearing completion in Beijing in which eight towers are connected by bridges at about the 20th floor, one of which contains a swimming pool.

Another major Holl design is Sail Hybrid, an expansion of a resort casino in Knokke-Hirst, Belgium.

In 1993, he collaborated with Vito Acconci on the clever flip-out design of the Storefront for Art and Architecture on Kenmare Street in SoHo, and more recently he designed the Higgins Hall Center at Pratt Institute in Brooklyn.

In May, the board of directors of the Port Authority of New York and New Jersey authorized the sale of about 7,300 square feet of vacant land on Tenth Avenue between 30th and 31st Streets to the Extell for $17,155,000.

The board also authorized granting Extell a perpetual light-and-air easement over an adjacent parcel of land of about 4,300 square feet for $500,000 and another easement for the construction and maintenance of a pedestrian skyway over an adjacent parcel owned by the authority for an amount to be negotiated of not less than $500,000.

Extell Development had acquired the low-rise building occupied by Stuart Dean, the building facade restorers, at 366 Tenth Avenue between 30th and 31st Street for $23 million.

The site lies within the Hudson Yards district.

Mr. Holl told Mr. Rose that Extell plans to erect a $2 million bridge to connect it with the cross-town section of the elevated railway that is part of the west and east sections of the rail yards for which the Metropolitan Transportation Authority recently put out a request for development proposals.

Extell has become one of the city's most aggressive acquirers of property in recent years.

It is converting the former Stanhope Hotel at 995 Fifth Avenue to residential condominiums and nearing completion of the 60-story condo tower known as the Orion on West 42nd Street and two high-rise towers on Broadway at 99th Street. It and The Carlyle Group agreed to acquire three apartments buildings designed by Costas Kondylis and land between 59th and 65th Streets near the Hudson River from a consortium of Hong Kong investors and Donald Trump for $1.76 billion and a recent report in the press indicated that Extell has commissioned Christian de Portzamparc to design the next three major apartment buildings in that complex facing the Hudson River.

In addition, Extell has a couple of development sites on West 57th Street.