Short answers, pulled from the story.
Shahjahanabad was built between 1638 and 1649 under the direction of the chief architect Ustad Ahmad Lahori. The Mughal emperor Shah Jahan ordered the construction of the new capital city to replace Agra in 1648.
The Shahjahanabad walls were originally constructed from mud and later replaced by red stone in 1657 to enclose an area with fourteen gates. These gates included the Nigambodh Gate, Kashmiri Gate, Mori Gate, Lahori Gate, and Ajmeri Gate, which controlled access to the city and symbolized the power of the Mughal rulers.
Shahjahanabad is home to the Jama Masjid, India's largest mosque, and the Gurudwara Sis Ganj Sahib, which commemorates the martyrdom of the ninth Sikh Guru, Guru Tegh Bahadur. Guru Tegh Bahadur was beheaded on the orders of the Mughal emperor Aurangzeb on the 11th of November 1675.
The British Empire took over Shahjahanabad in 1857 and shifted the capital to Calcutta and later to New Delhi. This event marked the end of Shahjahanabad as the capital of Mughal India and left the area to become the historic heart of the modern metropolis.
Shahjahanabad is home to Karim's restaurant, established in 1913, and the Paranthe Wali Gali, which was originally set up by Pandit Gaya Prasad in 1876. The area also features Khari Baoli, Asia's biggest spice market, and the Phool Mandi, the flower market of Daryaganj.