India, Aug. 24 -- The red sandstone walls are sculpted with calligraphy. Marble and black stone form flowers and stars. Every surface is as detailed as an illustrated page in an art book. Yet Delhi's most ornate monument is little known. Maybe because it stands in cramped and super-crowded Hazrat Nizamuddin Basti, ringed by private residences.

The tomb was built 460 years ago by Mughal noble Mirza Aziz Koka for his father Atgah Khan. Like many Delhi monuments, it had fallen into neglect. The interiors were originally covered with designs painted in red, blue and green. Much of that disappeared over time. Later repairs covered parts of what survived in. cement!

The Aga Khan Trust for Culture has completed a decade-long conservation of th...