Watch: HS2 viaduct built 'like giant Lego blocks'
Aerial video showed the first of 72 beams being lowered into place as part of a new railway viaduct for HS2.
The structure, crossing the flood plain of the River Thame near Aylesbury, Buckinghamshire, will carry the high speed line between London and Birmingham.
Engineers said it was the first of its kind in the UK to have all major elements manufactured off site and that each 25m-long (82ft) part would be moved into position "like giant Lego blocks".
HS2 Ltd's senior project manager Jennifer Lennon said: "We’re applying the latest approaches from across Europe to help us cut the amount of embedded carbon in our major structures and speed up construction."
