Towns and cities are mostly located in:

Plains
Shivalik Hills
Aravalli Hills
Thar Desert

Towns and cities are mostly located in plains. This is because plains are flat and have fertile soil, which makes them ideal for agriculture. Additionally, plains are often located near rivers or other sources of water, which is essential for human habitation.

The Shivalik Hills are a mountain range located in the northern part of India. They are a sub-range of the Himalayas and are much lower in elevation. The Shivalik Hills are not suitable for human habitation due to their rugged terrain and lack of flat land.

The Aravalli Hills are a mountain range located in the northwestern part of India. They are a much older mountain range than the Shivalik Hills and are much higher in elevation. The Aravalli Hills are also not suitable for human habitation due to their rugged terrain and lack of flat land.

The Thar Desert is a desert located in the northwestern part of India. It is the largest desert in India and is one of the driest places on Earth. The Thar Desert is not suitable for human habitation due to its lack of water and extreme temperatures.

In conclusion, towns and cities are mostly located in plains because they are flat, have fertile soil, and are located near sources of water.