The singer wore a black and white dress to perform her latest single Infinity at the opening party, held at the top of the building, which replaces the twin towers that were destroyed in the 9/11 terrorist attacks of 2001.

Other guests at the glitzy party, which was held 1,300 feet (396 metres) up, included rocker Jon Bon Jovi, Girls star Andrew Scott Rannells, singer/actress Bernadette Peters, and Scottish star Alan Cumming, who shared pictures from the event on his page.

The observatory opens to the public on Friday (29May15).