Owners of the iconic Gherkin building in the City of London have confirmed they are considering selling the tower.
The Gherkin is open to the public this weekend
Despite reports it is being sold for £600m, financial giants Swiss Re said while they were evaluating the sale, no decision had been made.
It also said it would occupy the building for the foreseeable future.
Officially called 30 St Mary Axe, the unusual building was built on the site of the bombed Baltic Exchange in the heart of the financial district.
The 40-storey tower cost £138m to build and was completed in 2003.
Designed by Lord Foster it maximises daylight and natural ventilation so that it uses half the energy typically required by an office block.
Each floor rotates five degrees from the last and the only curved piece of glass on the entire building is the very top piece.
As winner of the Royal Institute of British Architects (RIBA) Stirling Prize in 2004 it was described as "elegant and impressive".
The same year a reported 2,000 people queued to get a glimpse inside as part of the Open House initiative. It will be open again this weekend for Open House 2006.