In the years between the Second and Third Punic Wars, Rome was engaged in the conquest of the Hellenistic empires to the east and ruthlessly suppressed the Iberiann people in the west, although they had been essential to the Roman success in the 2nd Punic War.
Romans still harbored a bitter hatred for Carthage, which had nearly destroyed them in the 2nd Punic War. Sentiments ran so strong that the powerful statesman Cato ended every speech, whatever the topic, with the phrase that has become the classic example of the passive periphrastic in Latin grammar: Carthago delenda est! (Carthage must be destroyed!).
Meanwhile, Carthage had regained much of its prosperity through trade, further alarming Rome that a revived Carthage could again threaten them with war. When the Carthaginians refused to accede to the Roman demand that they abandon their city and move inland into North Africa, the Roman Senate declared war on them and the city was immediately besieged, beginning the Third Punic War.
The Carthaginians endured the siege from 149 to 146 BC until Scipio Aemilianus took the city by storm. When the Roman soldiers entered the city, they slaughtered all the inhabitants in a systematic house-to-house search.
The city with its harbor was destroyed utterly and the surrounding territory was supposedly sown with salt to make it unusable -- the sowing may have been merely a symbolic curse against Rome's defeated enemy, or the account may be entirely invented; it does not appear in the records of the war, and historians today dispute whether it actually happened