The surface of the Qutab Minar is described as "curved and angular". Let's break down this description and understand what it means.

Curved Structure:
The Qutab Minar is a tall tower located in Delhi, India. It was constructed using red sandstone and stands at a height of approximately 73 meters. When we say that the surface of the Qutab Minar is "curved," it means that the tower has a rounded shape. If you look at the tower from a distance or from the ground, you will notice that it tapers towards the top. The tower has five distinct levels or balconies, each of which is adorned with intricate carvings and inscriptions.

Angled Features:
In addition to its curved structure, the Qutab Minar also has "angular" features. This means that the tower has sharp corners, edges, and lines. If you observe the tower closely, you will notice that the surfaces of the balconies and the tower itself have angular shapes. These angles give the Qutab Minar a unique and visually appealing appearance.

Combination of Curved and Angular:
The Qutab Minar's surface combines both curved and angular elements. The overall shape of the tower is curved, with a gradual tapering as it ascends. However, when you look closely, you can see that the balconies, arches, and carvings on the tower have angular shapes. These angular features provide a contrast to the curved structure, adding complexity and beauty to the overall design.

Visually Appealing Structure:
The combination of curved and angular elements in the Qutab Minar's surface creates a visually appealing structure. The curved shape gives it a sense of elegance and grace, while the angular features add sharpness and intricacy. The contrast between these two elements makes the Qutab Minar stand out as a unique architectural masterpiece.

In conclusion, the surface of the Qutab Minar is described as "curved and angular." This means that the tower has a rounded shape with a gradual tapering, while also featuring sharp corners and lines in its balconies and carvings. This combination of curved and angular elements contributes to the visually appealing design of the Qutab Minar.