There are very few urban parks in the United States that can be compared to the grandeur of Europe's old and well planned out parks. Seville's Maria Luisa Park or Munich's English Gardens are simply some of the best in the world. I would, however, put New York City's Central Park up on that pedestal of world class parks.
One of the best walks in New York City is through Mall Area of the park. Ancient American Elm trees tower over you as you walk through this treasure of New York City. Catch it at the end of October and you'll be treated with the tree's golden colored leaves, ready for the approaching winter.