“Iron Pillar: “…In our opinion this pillar was made in the ninth century before (the birth of) Lord Jesus… When Rai Pithora built a fort and an idol-house near this pillar, it stood in the courtyard of the idol-house. And when Qutbu’d-Din Aibak constructed a mosque after demolishing the idol-house, this pillar stood in the courtyard of the mosque…
”Idol-house of Rai Pithora: “There was an idol-house near the fort of Rai Pithora. It was very famous… It was built along with the fort in 1200 Bikarmi [Vikrama SaMvat] corresponding to AD 1143 and AH 538. The building of this temple was very unusual, and the work done on it by stone-cutters is such that nothing better can be conceived. The beautiful carvings on every stone in it defy description… The eastern and northern portions of this idol-house have survived intact. The fact that the Iron Pillar, which belongs to the Vaishnava faith, was kept inside it, as also the fact that sculptures of Kirshan avatar and Mahadev and Ganesh and Hanuman were carved on its walls, leads us to believe that this temple belonged to the Vaishnava faith. Although all sculptures were mutilated in the times of Muslims, even so a close scrutiny can identify as to which sculpture was what. In our opinion there was a red-stone building in this idol-house, and it was demolished. For, this sort of old stones with sculptures carved on them are still found.
”Quwwat al-Islam Masjid: “When Qutbu’d-Din, the commander-in-chief of Muizzu’d-Din Sam alias Shihabu’d-Din Ghuri, conquered Delhi in AH 587 corresponding to AD 1191 corresponding to 1248 Bikarmi, this idol-house (of Rai Pithora) was converted into a mosque. The idol was taken out of the temple. Some of the images sculptured on walls or doors or pillars were effaced completely, some were defaced. But the structure of the idol-house kept standing as before. Materials from twenty-seven temples, which were worth five crores and forty lakhs of Dilwals, were used in the mosque, and an inscription giving the date of conquest and his own name was installed on the eastern gate…“When Malwah and Ujjain were conquered by Sultan Shamsu’d-Din in AH 631 corresponding to AD 1233, then the idol-house of Mahakal was demolished and its idols as well as the statue of Raja Bikramajit were brought to Delhi, they were strewn in front of the door of the mosque…”“In books of history, this mosque has been described as Masjid-i-Adinah and Jama‘ Masjid Delhi, but Masjid Quwwat al-Islam is mentioned nowhere. It is not known as to when this name was adopted. Obviously, it seems that when this idol-house was captured, and the mosque constructed, it was named Quwwat al-Islam…””

About antiquities of Delhi. Translated from the Urdu of Asaru’s-Sanadid, edited by Khaleeq Anjum, New Delhi, 1990. Vol. I, p. 305-16
Asaru’s-Sanadid