This is a tiny review originally from VT.com
The National Mosque (Masjid Negara) is an enormous mosque, as befits the capital. Non-Muslims are welcome to visit outside prayer times, though not allowed to enter the main prayer area. It has beautiful reflection pools around the outside, and is a spectacular building, inside and out – they don’t like photos, though, or at least didn’t when I was there. On the other hand, there isn’t really anything to do other than look.
If you want to visit, make sure you dress appropriately. The mosque will provide a robe and headscarf for women if you need to cover your arms, legs and head. They’ll do the same for men, in a fetching shade of lavender.
Address: Jalan Sultan Hishamuddin
Website: http://www.masjidnegara.gov.my/v2/ (only Malay)