The 2 inventions that surprised me the most (in terms of their early origins) were the battery and concrete.
I've seen a few ancient batteries (some of which dated back to the years when Egypt ruled the world) that some theorize were either used for "magic" or electroplating base metals with precious metals.
And until I actually went to Rome the first time, I didn't realize that the Romans (and possibly some of their predecessors) had concrete as a building material. Its used in their aqueducts (and other plumbing) and for reinforcing certain sections of the Catacombs.
As for the sliding doors-I remember first seeing that one in a book of "ancient magic" tricks. Alas, I don't own that one anymore, but I recall another one was a long metal half-cylinder that was submerged in a large pool. Underneath it, a small squad of soldiers awaited the signal to emerge from the water- their air refreshed by a tube and bellows. (AFAIK, it was only used for parties, not militarily.)
I've seen a few ancient batteries (some of which dated back to the years when Egypt ruled the world) that some theorize were either used for "magic" or electroplating base metals with precious metals.
And until I actually went to Rome the first time, I didn't realize that the Romans (and possibly some of their predecessors) had concrete as a building material. Its used in their aqueducts (and other plumbing) and for reinforcing certain sections of the Catacombs.
As for the sliding doors-I remember first seeing that one in a book of "ancient magic" tricks. Alas, I don't own that one anymore, but I recall another one was a long metal half-cylinder that was submerged in a large pool. Underneath it, a small squad of soldiers awaited the signal to emerge from the water- their air refreshed by a tube and bellows. (AFAIK, it was only used for parties, not militarily.)