"Seven Cities of Delhi and Mughal Architecture" Delhi by atufft

Situated as is in a wide open plain in northern India, Delhi has alternately served as a center of power and an invitation for invaders from the north. Aryan tribesman likely pushed Dravidian tribes south of the Uttar Pradesh plain during prehistoric times, at the same time the cast system was created as a way to maintain hegemony within a region already heavily populated and devoted to farming. According to Indian folklore, Delhi was to be the site of the magnificent and opulent Indraprastha, capital of the Pandavas in the Indian epic Mahabharata, founded around 5000 BC. Hindu texts also state that the city of Delhi used to be referred to in Sanskrit as Hastinapur, which means "elephant-city". None of the scattered archeological remains in the area clearly confirm establishment of a regional capital. However, the village of Indraprat, which was leveled by the British to establish New Delhi, is widely regarded as the same as the mythical Indraprastha, and archeological finds do show evidence of continuous settlement dating back some 2,500 years.

While the origin of the name Delhi is certainly old it remains obscure. Raja Dillu's Dilli, circa 100BC, sited just east of Lalkot, Dhilba founded by the Tomar Rajputs in circa 736AD, and the medieval town of Dhillika located near present day Mehrauli are three possible explanations. In any case, beginning in the 8th century, Rajput dynasties established fortified strongholds in the area of Delhi, but in 1192, the last of the Rajputs, the Chauhan king Prithviraj III, was defeated by Afghan invader Muhammad Ghori. Thus, the seven cities of Delhi actually begin with the establishment of the city as a capital in 1206, as the Delhi Sultanate under the so-called Slave Dynasty.

The Delhi government website lists and names the seven cities, only a few of which I was able to visit:

Qila Rai Pithora (built by Prithvi Raj Chauhan, near the oldest Rajput settlement in Lal-Kot)
Siri (built by Alauddin Khilji in 1303)
Tughluqabad (built by Ghiyasuddin Tughluq (1321-1325))
Jahanpanah (built by Muhammad bin Tughluq (1325-1351))
Kotla Firoz Shah (built by Firuz Shah Tughluq (1351-1388))
Purana Qila (built by Sher Shah Suri and Dinpanah built by Humayun, both in the area near the speculated
site of the legendary Indraprastha (1538-1545))
Shahjahanabad (built by Shah Jahan from 1638 to 1649, containing the Lal Qila and the Chandni Chowk).

Most of what we visited in Delhi was built by Mughal emperor Shah Jahan beginning in 1638 and now known as Shahjahanabad, or simply as Old Delhi. Red Fort and Mosque are the most outstanding of these. Outside of this area, however, is the UNESCO heritage site of Humayun's tomb, which we also visited. In addition to these excursions, we found Delhi to be an excellent place to shop for handicrafts from all over India, as well as from Tibet, Nepal, and even Bangladesh.