Much of the business was relied on by trade. That is how money came in.
Since Ancient Rome was at such an ideal spot it controlled much of the North, South, East, West trading.
Technology
Most Roman innovations were adopted by earlier Greek designs.
Roman civil engineering and military engineering constituted a large part of Rome's technological superiority and legacy, and contributed to the construction of hundreds of roads, bridges, aqueducts, baths,theaters and arenas.
Many monuments, such as the Colosseum, Pont du Gard, and Pantheon, remain as testaments to Roman engineering and culture.