What technological discovery (or rediscovery) was necessary for the completion of the dome atop Florence's Il Duomo in 1436?

A _____________ is a wedge-shaped block used in the construction of an arch.

The architecture of the Renaissance saw a resurgence of features from the architecture of which ancient civilization?

In an arch, the central piece of masonry that allows all the pressure to be placed throughout the arch is called __________.