Conservators have made a stunning discovery on the domed ceiling of the 16th century Sabz Burj, a Mughal monument near Humayun's tomb: hidden paintings in blue, yellow, red and white, and some even in gold. The conservators, working under the Aga Khan Trust for Culture and Archaeological Survey of India, and experts say this is the first time early 16th century wall paintings have been found on a monument in Delhi.