The Gherkin skyscraper in the City of London has been put up for sale.
The landmark building is expected to attract interest from around the world, joint agents Savills and Deloitte Real Estate said.
The 40-storey office tower is being sold by receivers after one of its joint owners, Germany's IVG Immobilien, filed for insolvency last year.
Co-owner Evans Randall said in April it was ready to invest further, but was unable to agree a new financial structure with IVG.
Agents said the building, whose distinctive curved profile has been a feature of London's skyline for a decade, could fetch in excess of £640 million.
Designed by architect Norman Foster, the tower houses about 20 firms, including reinsurer Swiss Re.