The Harmandir Sahib or the Darbar Sahi is more commonly known as the Golden Temple situated in the city of Amritsar, Punjab. It is the holiest temple (called Gurdwara) of the Sikhs. It was built by the sixth Guru Guru Arjun Dev, in the 16th Century when he completed the Adi Granth, the scriptures of Sikhism and then installed it in the Gurdwara. One great thing about this Gurdwara is that any one of any religion can go and worship. It is estimated that 100,000 people visit the temple every day. I highly recommend visiting the temple in Amritsar if you happen to be visiting North India.
Here are some pictures of the Golden Temple sent to me by a friend.