Ms Patil's new address in the Capital, a temporary one till she moves to Pune, is 2, Tughlak Road. Prime Minister Manmohan Singh, Sonia Gandhi and all ministers were present to bid her farewell. (In Pics: Pranab Mukherjee takes over as 13th President of India)
Mr Mukherjee took oath at exactly 11.38 am in the Central Hall of Parliament, familiar ground for him as an MP for over 40 years. He said, "I, Pranab Mukherjee, do swear in the name of God that I will faithfully execute the office of President of the Republic of India, and will to the best of my ability preserve, protect and defend the Constitution and the law, and that I will devote myself to the service and well-being of the people of India."
He then swapped seats with Ms Patil and was given a 21-gun salute. He signed a register and rose to speak at a rostrum adorned with purple orchids. Mr Mukherjee made a powerful speech, speaking about the problems of hunger and global terrorism; he spoke about democracy and secularism; he spoke about his role as the protector of the Constitution, above all politics. The President spoke in English and ended with Jai Hind. Vice President Hamid Ansari read out a Hindi translation of the beginning and end of the President's speech. (Full text of Pranab Mukherjee's speech)
Mr Mukherjee, 76, has worn a black sherwani with white churidar today, not the usual suits or dhoti that he prefers. His close aide Pradyut Guha said he spent a quiet Wednesday morning with his family at 13 Talkatora Road, his Delhi home for many years and then left in a Mercedes S 600 sent by the government. He visited Rajghat, then Rashtrapati Bhavan and then finally made his way in a Presidential convoy to Parliament House alongwith Ms Patil. (In black sherwani and Mercedes, Pranab Mukherjee visits Rajghat)
Before leaving home this morning, Mr Mukherjee took the blessings of Lord Tirupati - he had visitors who brought him prasad from the Andhra Pradesh temple. Mr Guha says he expects him to be a "people's President." (Special Feature: From Poltu to President in two hours)
The Indian Air Force has activated its air defence shield in and around the capital. Such security cover is provided during events such as the Independence Day and Republic Day. Services at three of Delhi's Metro stations - Central Secretariat, Udyog Bhawan and Khan Market - were suspended from 9 am to 11 am due to security reasons.
Lots of people have come to Delhi from Mr Mukherjee's West Bengal for the swearing-in ceremony of the first Bengali President. Bongo Bhavan in New Delhi is full of visitors and Mr Guha said many of them were disappointed as the government had issued very few cards for the swearing-in ceremony. "Lot of Bengal leaders came, Bengal MLAs came, they didn't get cards so they're very unhappy; they're crying, literally. I told them to see it on the TV. I am also going to see on TV," he said.
Among those at the ceremony was Mamata Banerjee, West Bengal CM, seated among other Chief Ministers. She landed in Delhi on Tuesday night and drove straight to Mr Mukherjee's home. Ms Banerjee had initially opposed Mr Mukherjee's nomination as the UPA candidate and then said she was voting reluctantly for him.
One of Kolkata's most famous imports to Bollywood, Mithun Chakraborty, who has been a mascot for Mr Mukherjee, attended the ceremony too. About 25 family members were also among the 100 odd personal guests of the President elect.
Mr Mukherjee, who was the UPA's candidate for the presidential poll, won the election quite comfortably with 69.31 per cent votes, very close to the 70 per cent that his poll managers had promised he would. In absolute numbers that meant 7,13,937 votes of the total 10,29,924 valid votes polled. This included a windfall from cross-voting by MLAs in BJP-ruled Karnataka. In comparison, the BJP's man, Purno Sangma, got the other 30.69 per cent and is still crying foul.
Up ahead lie tough tasks for Mr Mukherjee. There are more than 10 petitions sent by prisoners on death row to the President's office, asking for clemency. Among them, that of Afzal Guru, convicted for a terror attack on Parliament in 2001, a brazen assault in which 12 people were killed when Parliament was in session. The new President will have to decide what becomes of these mercy petitions, some of which have major political ramifications. For example, Balwant Singh Rajoana, who is in jail in Punjab for the assassination of former chief minister Beant Singh, is treated as a martyr and paid lavish tribute by the Sikh clergy.
The President is also likely to have a huge imprint on the political future of the country in 2014, when the general elections are expected to yield a hung Parliament. The President could then have a casting vote to decide who should come to power. He also has the right to dissolve a deeply-fractured Parliament, if that's what the results deliver.