In the later part the capital city of the Delhi Sultanate witnessed monuments built in this style within and around it. It started with the Turkish Slave dynasty building the Qutub Minar in 1192 and the Quwwat-UL-Islam mosque in 1193 built adjacent to it. The North India was successively ruled by foreign dynasties in the centuries that followed which in resulted in the growth of the Indo-Islamic architecture. The style that prevailed before this new style of architecture used to make use of pillars, lintels and beams. With the introduction of the new architectural style, with its beams and arches, the accuracy in construction style was brought about which eventually got patronage of the great Mughals. The Indian architectural styles were also incorporated, especially Rajasthani architecture, that included balconies, kiosks, pendentive decorations, and corbel brackets. This incorporation resulted in a distinct style of architecture known as the Mughal architecture which went ahead to last for a lifetime as a legacy of the four centuries of the Mughal rule. The white marble and red sandstone combination were seen in the tombs and mosques of the Delhi Sultanate. It was most distinct in the Alai Darwaza at Mehrauli in the Qutub Complex built under the Khilji dynasty in 1311 AD.
There are two lofty double Storeyed entrances on the south and west to the high rubble built enclosure, with a height of 16 meters and rooms on both sides of the passage and small courtyard on the upper floor. The six sided star that adorns the main gateway on the western side also used as an ornamental cosmic symbol on the main tomb structure. It is generally seen that a mosque is present near a royal tomb, like in the Taj Mahal, but here it is missing conspicuously. There is the tomb of the favorite barber of the Emperor known as Nai ka Gumbad in the enclosure. The tomb is built of red sandstone and rubble masonry and has used while marble for cladding material and flooring, door frames, lattice screens, eaves and the main dome. It spreads over 12,000 square meters and stands on a vaulted terrace 8 meters high. It has a square design essentially but is chamfered at the edges that makes it look octagonal to make ground for the design of the interior structure. The plinth that houses over 100 gravestones is made with rubble core and has 56 cells all around it. The whole structure is a few steps high on a raised platform.
Drawing inspiration from Persian architecture, the tomb is 47 m high and 91 m wide. It is the first building to make use of a Persian double dome on a high neck drum, measuring 42.5 m topped by brass finials ending of 6 m in the form of a crescent which is commonly seen in Timurid tombs. The dome is double layered, the outer layer is the white marble exterior while the inner layer supports the interior cavernous volume. The exterior dome is pure white marble contrasting the rest of the monument which is covered with red sandstone with detailing by white and black marble and yellow sandstone. This breaks the monotony.
The exterior is simple and symmetrical in design which contrasts the complex floor plan in the interior. The inner chambers' floor plan is square nine fold plan wherein 8 vaulted two Storeyed chambers radiate from the double height domed chamber in the center. It has an entrance Iwan at the south that is little recessed and other sides have intricate Galois covering them. Beneath the white dome in a hujra is the sepulcher, octagonal in shape, that is the burial chamber consisting of a single cenotaph of Emperor Humayun, aligned as per the Islamic tradition on the north south axis, with the head placed in the north and the face is turned sideways in the direction of Mecca. The actual burial site of the Emperor Humayun is in an underground chamber beneath the cenotaph that we can see. It has a separate passage from outside the main structure which remains closed to public viewing mostly. We find this burial technique along with pietra dura, a marble and even stone inlay ornamentation in different arabesque and geometrical patterns to be seen all over the façade, to be a significant legacy of this type of architecture. It was seen in later mausoleum built during the Mughal period. An example is the Taj Mahal which has twin cenotaphs and the same pietra dura technique of ornamentation.
The symbolic mihrab design which is over the central jaali, facing west in the direction of Mecca is also a feature of the main chamber. The Surah 24, which is traditionally inscribed over mihrabs is absent in this mihrab. It is meant to allow direct entry of light in the chamber from the Qibla direction, raising the status of Humayun over his rivals and bring him closer to the God.
This chamber has high ceiling and is surrounded by four octagonal chambers that are positioned diagonally along with arched lobbies that lead to them and also connects them. Added to it are auxiliary chambers four in number that suggest that this tomb was built to serve as dynastic mausoleum. Collectively the 8 side chambers offers not only a passage to the circumambulation of main cenotaph (a practice that is common in Sufism and seen in mausoleum of many Mughal emperors) it also tries to reflect the Islamic cosmology's concept of paradise. All main chambers have eight small chambers each that radiates from them. Thus, we see that there are 24 vaulted chambers in the in the symmetrical ground plan altogether. There are cenotaphs of other members of the nobility and the royal family in the small chambers within the tomb's main wall. The cenotaphs of Hamida Begum and Dara Shikoh are prominent among them. In all there are more than 100 graves inside the complex. Many are on the first level terrace and has earned the title of "Dormitory of the Mughals" due to the fact that the graves are not inscribed and it is difficult to ascertain their identity.
It is the first building to use the unique white marble and a red sandstone combination. It has included many elements of Indian style of architecture like the small chhatris that surround the central dome, originally from the Rajasthani style of architecture and covered with blue tiles.