London's Tower Bridge

This is one of London's best-known landmarks, but no photos of it being built were known, until recently -- coinciding with the 125th anniversary of the bridge's foundation, 50 sepia photos were handed in, found in a skip for dumping. They reveal in incredible detail the ingenuity behind the bridge.

The unique pictures, dating back to 1892, document the construction the iconic bridge, which at the time was a landmark feat of engineering nicknamed "The Wonder Bridge". The discarded pictures, which were retrieved by a caretaker who was looking after a building being turned into flats in 2006, have spent the last five years in a carrier bag underneath his bed.  The 59-year-old, who wishes to remain anonymous, said that after the occupants of the Westminster office building moved out, the album and a number of documents were thrown into a skip outside. He said, "I took the ledgers to the Tower Bridge Museum because I thought they might have some historical value." Mr Berthoud, an expert in the history of London who gives guided tours around famous landmarks including Tower Bridge, said he was gobsmacked by the haul. Memorable scenes include turn-of-the-century labourers taking orders from a site foreman in a bowler hat, and a shot of the bridge's original steam-powered engine room, which could open the bridge in less than a minute.

The sturdy steel frame of Tower Bridge can be seen, before it was covered with its distinctive stone-cladding. The bridge's original architect, Horace Jones, wanted to clad the bridge in brick, however, following his death he was succeeded as architect by John Wolfe-Barry who decreed the bridge should be clad in stone. The records include details of the materials used in the bridge's construction and what they cost.

Tower Bridge took eight years to build and at the time was a landmark feat of engineering, combining elements of a suspension and high level bridge, and a bascule which allows it to open for ships to pass. It is the only bridge over the Thames which has never needed to be replaced at some point. (thanks to Peter for sending this in)