The buildings outside the boundaries of your park are unlocked as your park achieves higher levels. The appreciation hearts collected from happy thoughts are currency for these buildings, such as activating the Peep Train at the front of the park.
The Casino has a wheel-spin game where you can win prizes. The first spin each day costs appreciation hearts, but tickets are the price for subsequent spins. The Trading Fair acts as an exchange. Trade your surplus cards and appreciation hearts for cards of greater value. For example, common cards can be exchanged for a rare card. The Mall is a place to purchase cards with appreciation hearts, coins, and tickets. The Heliport is similar to the Mall, but there’s a delay between ordering and the delivery of your order.