Bridges Over

How did they build stone bridges over huge rivers, like the Danube, before they had heavy machinery?
Likely they used a variation of the ancient Roman method of building arches supported by wooden frames until the keystone (at the top of the arch) could be inserted giving the arch its own durable strength.
Tagged as:
bridges over east river,
bridges over madison county,
bridges over madison county quotes,
bridges over ohio river,
bridges over poverty,
bridges over the hudson river,
bridges over the seine,
bridges over time,
bridges over toko ri,
bridges over troubled waters