The two most significant innovations in building design introduced by the romans were the which made construction of the pantheon possible.

The answer to this question is the ARCH and CONCRETE. Arch is a curve structure that was used by the Ancient Romans. Arches have different forms that produce vaults and arcades. While concrete is a composite material that is formed by mixing of cement and by sand, gravel, or stones. 

imperialism is a type of government that seeks to increase its size, either by forcing (through war) or influencing (through politics) other countries to submit to their rule. the sun never sets on the roman empire, or so went the saying when rome controlled the majority of europe 2000 years ago.