Centre Square, the 1500 Market St. office complex well-known for Claes Oldenburg's giant Clothespin art sculpture in its front plaza, was sold for $328 million this month to Nightingale Properties, a New York-based real estate investment company, CBRE Capital Markets announced Tuesday.

The sale of the 1.76 million-square-square-foot complex, which consists of a 36-story east tower and a 43-story west tower, marks the end of a more than yearlong search for a buyer. In March 2016, Chicago-based Equity Commonwealth put the property on the market. The sale was completed July 14, CBRE said, with the complex 91.2 percent leased.

According to CBRE, the sale is the largest office transaction based on square footage in the city's history. Nightingale Properties has plans to extensively renovate to the property, which was built in 1974, CBRE said.

Current tenants include the University of Pennsylvania Health System; Towers Watson, a global advisory and broking and solutions company; law firms Dilworth Paxson and Saul Ewing; Public Health Management Corp.; and Radian, a mortgage insurer. A 450-car parking garage and a 41,000-square-foot retail component with shops and restaurants are also located in the complex. Nightingale Properties has retained CBRE to continue on as leasing agent.

"Centre Square is a major part of Philadelphia's fabric and attracted investor interest and capital commitments from around the globe," said Robert Fahey, executive vice president of CBRE. "The asset sits across from Dilworth Park and City Hall and above the mass-transit network. It is the best located set of office towers" in the business district.

According to its website, Nightingale Properties said it "acquires high-potential commercial real estate … then manages the asset to ensure it achieves its highest and best use." It currently owns three other buildings in the Philadelphia market: 1500 Spring Garden, 1835 Market St., and 1635 Market St., according to its website — all multistory office buildings in Center City. Previously, the group purchased 1700 Market and then sold it after property improvements.