The Bukit Nanas Reserve is the only original rainforest remaining in metropolitan Kuala Lumpur, and is still home to pythons, monkeys, and other creatures of the wild. Within Bukit Nanas, you'll find the best view in the city, lauded as the second highest free-standing tower in the world, the Menara KL Tower. Located on a hill, you'll get an amazing view from the observation deck and revolving restaurant, as well as access to a number of fun activities (an F1 flight simulator and other rides).
Believe it or not, this is a higher view than the nearby Petronas Towers, which are the tallest twin towers in the world. A basic ticket package that includes the observation deck costs 45 RM (about $14 USD) for adults.