Explanation: The Indus Valley Civilization, which flourished between 2600 and 1900 BCE, is renowned for its advanced urban planning and infrastructure. The cities of Harappa and Mohenjo-Daro are prime examples of this civilization's architectural and engineering prowess. The urban planning of these cities was highly organized, with features that were quite advanced for their time.
One of the most notable characteristics of Indus Valley cities was the presence of fortified walls. These walls were constructed using mud bricks and served as a defense mechanism against potential invaders and wild animals. The walls were an integral part of the city's security system and were a testament to the civilization's understanding of urban defense.
The cities also featured a well-planned grid system with wide and straight roads. These roads were laid out in a grid pattern, intersecting at right angles, which facilitated efficient transportation and movement within the city. The grid system was a hallmark of the Indus Valley Civilization's urban planning and demonstrated a sophisticated understanding of city layout and design.
Houses in the Indus Valley Civilization had flat roofs, which were used for various purposes such as drying grains, storing goods, and as living spaces during hot weather. The flat roofs were constructed using wooden beams and mud plaster, providing a practical and functional living space.
Another significant feature of the Indus Valley cities was their advanced drainage system. Covered drains ran along the streets and were connected to individual houses, allowing for the disposal of waste and sewage. This drainage system was a testament to the civilization's concern for hygiene and public health.
However, the use of wind mills to produce electricity is a modern concept and was not present in the Indus Valley Civilization. The Indus Valley Civilization existed long before the invention of electricity and wind mills. This option is an anachronism and does not fit with the historical context of the Indus Valley Civilization.
In summary, the Indus Valley Civilization was characterized by fortified walls, well-planned roadways, flat-roofed houses, and a sophisticated drainage system. The use of wind mills to produce electricity is not a characteristic of these ancient cities, making it the correct answer to the question.