Why is my city now attacking as a catapult?

Question

I'm playing Civilization 5 and, out of a sudden, my city started to attack as a catapult. It used to throw arrows, now it throws rocks. What did I do?

Answer 1

The technologies in Civ 5 are broken up into various eras. The first time you research a technology from a new era, you'll see some graphics update. This means that the city will change in appearance in accordance to that era and the city long range attack with it.