Flames swept through the Windsor Tower, a skyscraper in the heart of the financial and business district of Madrid, late on Saturday 12 February 2005, completely destroying the 32-storey building.
It was 11.30pm when the fire broke out on the 21st floor. However, investigations showed that it had been burning for some time before it was detected.
The building's fire alarm system was not working as it was in the process of being updated to comply with new fire safety laws, having been installed when the tower was completed in 1979.
The fire quickly spread upwards, affecting first the eight floors immediately above the 21st, where flames were visible. Broken windows and debris started to fall to the ground from the top floors.
The official investigation never established the cause of the fire although one theory was that an employee had been smoking in the offices of consultants Deloitte where the blaze started. However, the investigation never confirmed whether there were people in the tower at the time or not.
Unanswered questions about the fire have fed a number of theories over the years.
There were no casualties although three firemen were treated for smoke inhalation.
Madrid's main El Corte Inglés store had to be evacuated of all cleaning staff on the Saturday night.
Eighteen fire engines were the first to arrive, followed by a further 15 vehicles. It was not until after 5pm the following day, however, that the flames finally died down.
A large area around the building was cordoned off, which prevented around 600,000 office and shop staff from going to work and brought all commercial and financial activity in the Azca district to a standstill. El Corte Inglés remained closed for several weeks.
A crisis committee set up by Madrid City Hall announced the following Monday that the tower would be demolished.
The demolition of Windsor Tower was completed in August 2005, and a 23-story replacement called Torre Titania was built from 2007 to 2011.