Depending on whether you want man-made or natural sights there are quite a few possibilities for day-trips to get you out of Kuala Lumpur.
One of the more popular and nearest "natural" sights are the Batu Caves.
One of the surprises of Kuala Lumpur is that you don't have to go very far to be out in the country-side ( calling it "jungle" sounds a bit too exotic) and see lots of greenery.
Batu Caves are about 15km outside the city on the outer-ring road and are the focal-point for over a million Hindus during Thaipusum,at other times of the year it's less busy but they are on the tour-group day-trip itinerary and are a popular destination.The cave complex is in a huge limestone outcrop and offers an interesting excursion and some fresh air.A climb of 270 steps leads you into the vast main cave which is where the Thaipusam pilgrimage ends.There are a few other caves to visit,some with interesting statues and sculptures inside.
To get to the caves ,you can get a taxi for about RM 25 or a bus for about RM2 with http://www.rapidkl.com.my/