To unlock main destinations, win shows!  You will need to earn every souvenir and trade those in for a passport to the next destination.
 
Bear in mind, to progress through the levels in each destination you need to collect enough cash, but once you've gotten to the last level, if you still don't have enough souvenirs, you won't be able to progress.
 
You can see how many souvenirs you have / need by checking your Passport.
 
If you've already made it to the last destination, firstly, CONGRATULATIONS! Secondly, please bear with us while we work on the next one! We're always developing new destinations to keep our most dedicated players busy. Unfortunately we're unable to tell you exactly when the next destination will be available, but trust we'll get it to you as soon as we can!