The 355th death anniversary of Mughal emperor Shah Jahan is being observed at the greatest of all monuments he built that is the Taj Mahal.
Tens of thousands of devotees thronged the 17th century marvel especially for the three-day event that began on Friday.
During this period, people pay homage at the graves of Shah Jahan and his wife Mumtaz, in whose memory the Taj Mahal was built. The graves otherwise are not open for public viewing.
Security personnel expect a big rush until Sunday. Entry to the Taj is free Saturday and Sunday.
Prince Yakub Habeebuddin Tucy from Hyderabad, who claims to be the last descendent of the Mughal dynasty, will participate in the Urs.
One of the organisers, Tahiruddin Tahir, said a record 450-metre 'saptrangi chadar' (multi-coloured sheet) will be offered at the graves as part of a ritual.
Sandalwood powder will be sprinkled on the graves.
However, ambiguity about the year of Shah Jahan's death continues.
The Uttar Pradesh government website mentions 1666 as the year Shah Jahan died, making this the 344th anniversary. But the organising committee is celebrating it as the 355th Urs.
The Taj Mahal, India's biggest tourist draw, is located about 200 km south of New Delhi.