What architectural features did the romans first create and use in their buildings?

The Romans used the Arch and Dome for buildings mostly, for example the aqueducts.

Klemens von Metternich was NOT directly involved with the unification of Italy.

In the Concert of Europe a series of alliances among European nations within the nineteenth century devised by aristocrat Klemens von  Metternich to forestall the natural event of revolutions. Great Britain, Russia, Prussia, and Oesterreich united to satisfy sporadically to debate interests in maintaining peace.