Kampung Baru and Chow Kit provide a real authentic atmosphere into a traditional and old part of Kuala Lumpur. You can see the city encroaching into this neighborhood but surprisingly this old Malay settlement has resisted being overrun with modern buildings and coffee chain stores.
It's a bit out of the way for the normal tourist, but is conveniently reached through the Chow Kit Monorail station and can be combined with a trip to Titiwangsa Lake.
Chow Kit Market is one of the largest and oldest fresh produce markets in K.L. and is a great, real life experience to walk through. Walking along Jalan Raja Alang offers great small eateries to test out real Malaysian food and gives an opportunity to explore the Kampung Baru Mosque as well as the Sikh temple, Guru Nanak Darbaar Gurdwara Sahib. It was said to be open to worshippers only, but behaviour and attitude is all that it took me to be allowed inside for a free tour.
Kampung Baru also still offers glimpses at small traditional wooden houses, local shops and restaurants and for me, one of the friendliest crowd of locals I have ever met on my street walks.