I like the idea, I think it has a lot of potential, but from what you wrote in how it works part (if I understand it correctly) it seems a bit limited.
I suggest allowing many chat rooms in the same spot, I also suggest that instead of the chat room creator having to pay the "location domain" rent, google maps could add this feature to a subscription-based upgraded version of google maps. So anyone having "google maps premium" could see, use and create chatrooms on google maps. That's if there would really be a need for additional income to sustain this, maybe google could include the function for free.
That way anyone wanting to start a chat room in a certain spot could do this and invite others to chip in. Chat rooms would be initially marked with signs similar to location/object markers now used in google maps. Seeing a "chat room" marker would mean that there is one or more chat rooms in that specific spot. Upon clicking on the marker you'd see a list of chat rooms present in that spot, you could use a search function to find a specific chat room in case there were a lot of them (e.g. on the Eifel tower).
When you'd enter a specific chat room in that location, you'd see something similar as shown in the cover image of this idea, you wouldn't see the mess of other chat rooms. Chat rooms could be both private and public, the creator would choose that through chat room settings.