The Park is a place for your people to gather and enjoy nature or hold large scale public events. The Park allows you to throw parties for your citizens to increase their happiness. The more varieties of foods you bring to the party the more happiness is produced. Increasing the level of the park also increases the happiness produced by parties, but not nearly as much as extra food types do.
Quoting JT from the forum: "This is an oversimplification of the formula, but the happiness produced by a party of a level one park is 3000 times the number of food types that you have available in quantities of 500 or more. So if you have 4 food types, then the party would be worth 12,000 happiness. If you had 6 it would be 18,000, and so on."
Keywords: Happiness Buildings