The typical Central City should include at least one of these features:
A location like Eisenstadt often represents a transformative moment in the campaign. Here, the protagonists might find incomplete answers to some questions, meet new allies, and, perhaps, buy some brand new equipment and a flying or seaworthy transport.
The Central City is also a great opportunity to introduce new threats and start the second half of the campaign.
Eisenstadt is the largest city in the region, distinguished by its high technological level, easy access to numerous resources, and an ambitious and individualistic society: fertile ground for a Villain. This kind of location tends to present strictly humanoid antagonists, such as greedy merchants, callous industrialists, and alchemists or inventors willing to accept daunting risks in the name of progress.
These questions are designed to prompt roleplaying encounters and build tension: