Help with place names — fiction

Sorry in advance if this is not the right place to post it, but I didn't know where else to put it.

So, I'm currently planning a story that's inspired by the life of PuYi, the last Emperor of China.

The setting is a fictional insular nation in Asia, and it's framed through the memoirs of the last boy ruler of this kingdom after everything fell and he needs to process his very unusual life.

I am struggling with names for the Kingdom — at first I thought of Tiandong (which I might use for the capital), but I don't know if it's a good name.

I'm Brazilian, I've recently started to read more into China's History and I don't speak Chinese, so I'm sort of a loss here !

If anyone could help me with place names, character names, etc, that would be very helpful !