Princess, you are correct. There is a fifth one. On my board it shows up closer to the bottom right and relatively close to the other four new expansions. It is 19 lanterns, 160,000 coin, and no expansion permits needed.
As someone indicated, of the four new expansions that are grouped together, the first two don't require expansion permits. The third one requires 3 of them.
Had 100 lanterns going into this event, but no expansion permits, so will be here for awhile before I can find out what the fourth one requires.
Surely was fun though, today, to be able to open three new areas in my queendom!
Thank, S8, for a new addition to the story line! And mermaids, none-the-less! What a winning idea! After-all, who doesn't adore mermaids?!? Yay!!