Some of the Park Options
The parks come in a variety of different sizes, and you can join them together by selecting your park and clicking the edit button to add another park to it. They also are available at a variety of prices to suit all budgets with varying hourly costs and varying attractiveness to certain populations and average expected visitor numbers, so check through and find the best one for your situation.
Adding a Community Park
You'll definately be prompted to start adding parks to increase the attractiveness of your residential zones to higher wealth sims. In my opinion, the largest parks are the best, I find the small parks awkard to fit into established blocks. Although if you select a plopped park and use the edit feature you can extend most parks to make them bigger.
Adding Parks gives a positive effect on residental and commercial zones
Adding More Parks
There's nothing like adding a few more green spaces to your urban landscape it can do wonders for the denisty of your population and really adds to the happiness of the residential sims around a park. Once your City has reached a significant size hopefully you would have added more than one park! It will seriously help your City density and overall happiness. Remember to place them close to residential and commerical blocks after all Sims do like to visit parks when going shopping or when visiting your City.
There are a vast array of parks available to be utilised (see the tree icon), as soon as you start the game. The largest and best parks are unlocked only when you have a department of culture in the region. You can also use the parks tool to forest and de-forest areas. Parks have the function of raising happiness and wealth around commercial and residential zones. However in failing cities you'll also find they become homes to homeless citizens of your City. There are many categories of park, such as formal - with it's fountains and walkways, sports - with it's football and baseball pitches, skate parks and ice rink options, and natural which offers a variety of plain parks, some with parking facilities.