This picture is just a glimpse of the intricate carvings and skills of the Hindu Artisans - who were then asked by the king to make an islamic "arch". Please read the introduction to this album for the background.
Domeless tomb of Sultan Shams-ud-din Iltutmish, or Altamash (1211 - 1236 AD). He was the third Muslim Turkic sultan of the Sultanate of Delhi and the third ruler of the Slave dynasty. This tomb was built by Hindu masons and artisans and they built the arches in Trabeate style which they invented when they were pressed to furnish the same. Similar arches are present in other original structures of the Qutub complex. Trabeate arch has its disadvantages and the style very soon disappeared after Altamash - giving way to Arcuate arch which was more robust and flexible for creating derivative structures like a dome. Arcuate arch was actually invented by the Romans and the style soon spread through the Mediterranean, Middle East and Central Asia from where India's Turkish invaders came. Though, it was just a matter of time when Trabeate style came back with a vengeance at the hight of Mughal empire, when some of the most beautiful arches of India were created.
The above is an illustration of the way Trabeate arches are built. Since stones were the building material in ancient times (unlike steel today); Trabeate style came across as an inefficient design. Stones (like bricks) are poor against stress points. Drop a stone from a few meters and it will break (like bricks) but they are excellent against compression. Stack one on top of the other (like bricks again) and nothing will happen to them. Hence, Trabeate style required careful choice of material that could have withstood the stress thrown at them - not only making the project costly but also posing a problem for the design scalability. Most of the structures in Qutub complex with Trabeate style of arches are still standing (it being a sultanate project, was best quality), however, it is quite possible that any other structure created with same style during that time period has long vanished.
The above is an illustration of the Arcuate arch which was invented by the Romans and which finally arrived in India via its Turkish invaders. As stated in the illustration of Trabeate arch, stones are excellent against compression (as against stress) and the Arcuate arch exploits this design method. Arcuate arch is also known as a "True Arch". This was to become a staple for all the arches, big or small, sultanate or common, in the times to come after the slave dynasty in India. The true arch quickly became secular and later many of the Hindu palaces and forts also employed it in various shapes and sizes. This style also moved westwards and almost all of the western architecture employed this style of constructing arches (including the Raisina Hills of Lutyens Delhi).
Outer Corridors of Balban's Tomb. Ghiyas ud din Balban became the sultan of Delhi in 1266 AD. He was a courtier at the time of Razia Sultan. The very first "True Arch" was built in India in this tomb. Lying on the edge of Mehrauli Archaeological Park, the tomb itself is in a ravaged state but the very first true arches are still standing. Possibly built in 1287 when Balban died.
Structure as viewed from the inside of Balban's tomb. It is speculated that this tomb had a dome but the same does not exist anymore. Notice the True Arch towards the right-top. The pressure exerting triangular keystone is clearly visible at the top.
The "True Arch" technique was extended to create a dome (as depicted above). It indeed appears to be true as there is no dome to be found in India earlier to when true arch was introduced to the land. Trabeate domes can be created but the technique is very inefficient. In fact, there are two shallow domes at the entrance of Quwwat-ul-Islam Mosque in the Qutub Complex built using Trabeate style and looking at the unimpressive shallowness of the domes, one can understand why Trabeate went out of the favor at that time.
This is a very interesting building. It is not famous at all. It is in a corner of the Salimgarh Fort to the north-east of Red Fort in Delhi. SalimGarh Fort is a very small enclosure (comparatively) that was built by Salim Shah Suri, son of Sher Shah Suri in 1546 AD. Yamuna used to hit this fort and bifurcate into two, encircling the fort, one stream used to touch the Red Fort of Delhi (where the current Ring Road of Delhi is present). This fort was connected to the Red Fort of Delhi when Shahjahan built it and was typically used for storage and as a Jail. In fact it was used as a Jail till the British left India and freedom fighters of Indian National Army (INA) were also imprisoned and tortured in this fort from 1945 till India's independence in 1947. This fort also housed the battery and canons of the sepoys during the mutiny of 1857. As a result, this fort came under heavy canon fire of the British army and almost all the structures inside the fort were destroyed including the above structure. Though styled like a tomb, it appears this was a storage building (I could be wrong). Nevertheless, interesting point about this structure is the cross-section of the Dome that has been revealed due to its cannoning. The Arcuate or "True Arch" style of its dome is clearly visible.
Ruined dome and structure at the Salimgarh Fort. Please check the cross section of the dome in the earlier picture and also its description.
So what protects the keystone of a dome? The huge weight on top of the keystone of a dome is not only meant for aesthetic purposes but is also meant to exert a constant pressure on the keystone. This dome is of the tomb of Daulat Khan Khwaja Muhammad, built in 1506 during Sikander Lodhi's reign, adjoining "Rajaon ki baoli" in the Mehrauli Archaeological Park. Notice the blue Persian tiles that are an original while rest of the decorations of the dome are gone.
A different/creative style of employing a keystone to the arch by the British architects. Notice the red wedge on top of the arches. This building was erected by the British army in the Delhi Red Fort after clearing many fine Mughal Pavillions and structures of Mehtab Bagh (west of Hayat Bakhsh garden), after the mutiny of 1857.
The Islamic Arches in India were at the peak of their glory during the Mughal period, notably during Shahjahan's time. The arches in the above picture (Lahori gate of Delhi Red Fort) are of finest quality. Notice the Trabeate style of the main arch at the center-bottom. It is actually an engineering marvel, the weight distribution and balancing of the structure and not overly weighing down the red sandstones in the Trabeate formulation.
The Trabeate style cusped arches at the diwaan-e-aam of Delhi Red Fort. As mentioned earlier, Trabeate style was back with a vengeance and in its finest form during the Mughal period.
The Saawan pavilion (there is symmetrical Bhadon pavilion to the opposite) at the Persian char-bagh style Hayat Bakhsh garden of Delhi Red Fort. Furnished completely out of the best quality Makrana Marble, this is a very delicate and beautiful structure that says volumes about Mughal's attention to details. Notice the delicate cusped arches. Mughals at this stage actually dabbled with various styles of arches - Islamic style, British style, Bengal style, etc. In fact some of the structures in the Delhi Red Fort incorporate multiple styles in the same building, creating a very unique and delightful sight. Truly, ancient architecture in India was at its peak during this time.
"In excellence and glory it surpasses the eight-sided throne of heaven, and in luster and color it is far superior to the palaces in the promised paradise" - was how a court chronicler described the Rang Mahal of Delhi Red Fort. These are the most beautiful arches I have ever seen in my life. They are unparalleled. Indeed the cusped nature of it conveys such finesse in architecture that I long to shake hands with the builders and congratulate them on this immaculate work!