eli5: How did people build bridges over deep and/or dangerous water if they didn’t have the equipment to go under water?

Question

eli5: How did people build bridges over deep and/or dangerous water if they didn’t have the equipment to go under water?

In: 22

Answer 1

TLDR: boats

Suspension bridges at a basic level only required a rope to be pulled across a river, and that can easily be done with a boat.

Larger footings could be poured from a boat as well.

While there’s a lot of prep work and drilling down on a river bed for bridges today, it more ancient times they would likely have just floated a barge to the spot and dumped large quantities of gravel and large rocks to create a solid footing