The Greek authorities have begun using cranes to winch thousands of ancient sculptures housed in a museum on the Acropolis to a new museum below.
Over the next few months, 4,500 antiquities will be carried the 400 metres (yards) to the new site.
The marbles, most of which date from the Fifth and Sixth Centuries BC, have been insured for 400m euros (£280m).
Last week a number of unworked marble slabs were lifted off the hilltop as the system was tested.
When it came to start moving the real thing, the marbles were carefully packed in polystyrene and wood before being placed in metal crates.
Crews in three cranes moved a 2.3-ton section of the frieze which once adorned the hill's largest temple, the Parthenon.
Down below crowds had gathered to watch the historic event.
Once safely in situ, the crates were opened and the rich carvings inspected.
Greek officials hope the new site will boost the country's long campaign for the return of the Elgin Marbles.