There would be no rich families in the rich city. So before the renovation the city was poor rich. Because those rich people that live in the old city are not the rich people of the rich city, its the people of the abandoned city. The people that live in this abandoned city have used the iron found in the kingdom before the iron was rendered useless by the advancement of technology. Once they have entered the city they used this iron to manufacture spears. It's a lot of work to make a spear, to get the materials needed. Even if the people of the abandoned city doesn't want to work. They have very little to offer. But by the sword their city became rich.
Even after the industrial revolution and the advancement of technology more and more people moved to the abandoned city and settled throughout the city. The small houses became packed and large towering buildings arose. For every large modern skyscraper in the abandoned city there was a small home made out of wood. And while the rich city has very few criminals. The rich city has frequent kidnappings. These are used because the rich people has a lot of money. But the rich people of the rich city are still the poor people of the abandoned city.
The reason why the rich city is poor is because of the bureaucracy that stops the rich people from investing in the city. The only people that is rich in the rich city is the empty government. The rich people that live in the abandoned city are not allowed to leave to work in the rich city. So they are left to rely on their families to feed them and clothe them. They are left to do every day tasks that only need a very harsh and uneducated psychology to be done, but to do them well.
The rich city and the abandoned city is indestructible. For example it took the burning hut of the abandoned city two weeks to go down and two years to go up again. They have to be rebuilt from ground to top. One battalion of the military and one battalion of the scientists have been sent into the abandoned city to investigate the oddities that are going on there. The scientists don't want the memories of their past science be shown again. Tired of the relentless repetitiveness that was suffering in the abandoned city the military wanted to change the situation. But the scientists thought the military would destroy their research and the abandoned city. The two were fighting with classes and classist ideals. But they eventually they found the ones that caused both problems. However they also found out that the people of the abandoned city didn't know how to use the iron that was discovered in the city. One of the species that had come there to explore the abandoned city were the intelligent ones. The intelligent species had been there to explore this unexplored region long ago. So they had created a faction of people that were in constant communication with them (the intelligent species). They now know that the intelligent species have been in contact with the people of the abandoned city and have influenced them. But those intelligent species have never told the people of the abandoned city that they are the intelligent ones. The people of the abandoned city are simply working for the intelligent species like any other servant. They are sent as ambassadors to the world to spread the ideas of their master.