Unlocked rides not showing up in building list

[sammysawce]

A lot of rides that I have unlocked aren't showing up in the building list. For example; I just unlocked the Double Decker Observation Tower and when I go to build it's not there. Do I need to download anything for these to show up? 

[jensj12]

If you have a ride that uses the same track, it will show up as a vehicle for that ride. Check if you already have any other observation tower. It should list the (number of?) available vehicles at the bottom of the window. Alternatively, click the build button on the news message.