Hello Archon. It seems to me like a trapped city that has a lot of Hamippos out, so you see nothing if you scout the city, plus huge defences that are protected by Mamertines, so no political attack can pass. It is a common tactic of the big players because no one attacks their cities, so they use their alts to get easy PVP. Usualy, trap cities are low level and have fully upgraded Elysian towers. You might find who is behind this, if you check the Current defence rankings. If you want to do damage, use your light and heavy infantry, and a very good Javelineer guardian. Of course, you can always contact the Support and report the player, but if it is a trap city it is not cheating, just a strategy.