When in Kuala Lumpur, capital city of Malaysia, (KL for short), chances are your guided tour itinerary would include a visit to the Batu Caves.
Batu Caves is a limestone hill that has a series of caves and cave temples (Hindu) located on the fringe of the city center in Gombak, Selangor. In fact, it is along the stretch of MRR2 (Middle Ring Road 2, one of a number of highways in the Klang Valley). It is visible from the highway itself. That's how easily accessible it is.
Rising almost 100m above the ground, the Batu Caves temple complex consists of three main caves and a few smaller ones. The limestone forming Batu Caves is said to be around 400 million years old.. Wikipedia. 272 concrete steps up will take you to the main Temple Caves.
If you don't mind crowds or want to soak in some local culture, time your visit to Batu Caves to during Thaipusam, a Hindu festival that can see thousands making it to the caves either as devotees or plain visitors for a life-time experience. I kid you not. Kavadi-carriers are indeed a sight to behold.
Image source: Wikipedia