What caused the emergence of cities in Europe?

1. The fall of the Roman Empire, which left behind many cities with developed infrastructure, and therefore these remnants of the ancient heritage were the first to take the form of modern cities.
2. The need to defend against the raids of nomads, and just other neighboring cities.
3. The first feudal castles began to emerge in the 6th-7th centuries, and ordinary people settled around them, so cities began to arise.
4. The concentration of guild and manufacturing crafts required a special organization of municipal administration, which could arise only in cities.