I read last night that the conquest of Dacia (modern-day Romania) by the Romans around the early 100s A.D. was the most lucrative of them all for Rome.  The wealth brought back to Rome helped to fuel Trajan's massive building campaign, and the booty was so large that it lasted until the end of the reign of the next emperor, Hadrian.  My question – how on earth did Dacia get so wealthy?  And why did Rome not conquer the territory before Trajan?  If you compare a map of Roman territories at the death of Augustus in 14 A.D. and the empire at the death of Trajan in 116 A.D., you can see how Dacia was well within the geographical reach of Rome for some time.BTW, the maps are from an interesting site:http://www.roman-empire.net/maps/map-empire.html