The focus of Taj Mahal is the white marble tomb, which stands on a square plinth consisting of a symmetrical building with an iwan, an arch-shaped doorway, topped by a large dome. Like most Mughal tombs, basic elements are Persian in origin.
The base structure is a large, multi-chambered structure. The base is essentially a cube with chamfered edges and is roughly 55 metre on each side.
On the long sides, a massive pishtaq, or vaulted archway, frames the iwan with a similar arch-shaped balcony. These main arches extend above the roof of the building by an integrated facade. On either side of main arch, additional pishtaqs are stacked above and below. This motif of stacked pishtaqs is replicated on chamfered corner areas as well. The design is completely symmetrical on all sides of the building. Four minarets, one at each corner of the plinth, facing the chamfered corners, frame the tomb. The main chamber houses the cenotaphs of Mumtaz Mahal and Shah Jahan with their graves located on lower level.
The marble dome that surmounts the tomb is its most spectacular feature.
Its height is about the same size as the base of the building, about 35 metre and is accentuated as it sits on a cylindrical "drum" of about 7 metre high. Because of its shape, the dome is often called an onion dome (also called an amrud or guava dome). The top is decorated with a lotus design, which serves to accentuate its height as well. The shape of the dome is emphasised by four smaller domed chattris (kiosks) placed at its corners. The chattri domes replicate the onion shape of main dome. Their columned bases open through the roof of the tomb and provide light to the interior. Tall decorative spires (guldastas) extend from edges of base walls,and provide visual emphasis to the height of the dome. The lotus motif is repeated on both the chattris and guldastas. The dome and chattris are topped by a gilded finial, which mixes traditional Persian and Hindu decorative elements.
The main dome is crowned by a gilded spire or finial. The finial, made of gold until the early 1800s, is now made of bronze. The finial provides a clear example of integration of traditional Persian and Hindu decorative elements. The finial is topped by a moon, a typical Islamic motif, whose horns point heavenward. Because of its placement on the main spire, the horns of moon and finial point combine to create a trident shape, reminiscent of traditional Hindu symbols of Shiva.
At the corners of plinth stand minarets, the four large towers each more than 40 metre tall. The minarets display Taj Mahal's penchant for symmetry. These towers are designed as working minarets, a traditional element of mosques as a place for a muezzin to call the Islamic faithful to prayer. Each minaret is effectively divided into three equal parts by two working balconies that ring the tower. At the top of the tower is a final balcony surmounted by a chattri that mirrors the design of those on the tomb. The minaret chattris share the same finishing touches, a lotus design topped by a gilded finial. Each of the minarets were constructed slightly outside of the plinth, so that in the event of collapse, a typical occurrence with many such tall constructions of the period, the material from the towers would tend to fall away from the tomb.