There are several property types that would work under the category for "Entertainment/Public Assembly," depending on the size and services offered at the park:
- Stadium -> Stadium (Open)
- Stadium -> Stadium (Other)
- Recreation -> Other - Recreation
A small park with just lighting for night games, should use "Other - Recreation."
A large park with bleacher seating around a field(s), a concession stand, and rest rooms, should use "Stadium (Open)."
Something in between, could use "Stadium (Other)."