Haerappan civilization, also known as the Indus Valley civilization, was one of the world's earliest urban civilizations, flourishing in the Indus River valley from about 2500 to 1900 BCE. It was named after the modern-day town of Harappa, where the first archaeological discoveries were made.

- **Urbanization and Planning**
The Harappan civilization was characterized by well-planned cities with advanced urban features. The cities were divided into different sectors and laid out on a grid pattern, with wide streets and a sophisticated drainage system. The planning and organization of the cities indicate a high level of social and administrative control.

- **Trade and Economy**
The Harappans were skilled traders and had a thriving economy based on agriculture, trade, and craftsmanship. They traded with regions as far as Mesopotamia, using standardized weights and measures. They produced a wide range of goods, including pottery, jewelry, metalwork, and textiles.

- **Writing System**
One of the remarkable features of the Harappan civilization is their writing system, known as the Indus script. However, the script has not been deciphered yet, so the exact nature of their writing and language remains a mystery.

- **Agriculture and Technology**
The Harappans were advanced agriculturists and used irrigation techniques to cultivate crops such as wheat, barley, peas, and cotton. They also domesticated animals like cattle, sheep, and goats. Their technological advancements include the use of bronze tools and a sophisticated pottery-making technique called the wheel.

- **Religion and Culture**
The Harappan people had a complex religious and cultural life. They worshipped a variety of deities, including a mother goddess, a male deity often depicted as a yogi, and animals like the bull and the unicorn. The discovery of numerous seals with animal motifs suggests the presence of a unique religious symbolism.

- **Decline and Legacy**
The Harappan civilization declined around 1900 BCE, possibly due to environmental factors such as climate change and the drying up of rivers. The exact reasons are still debated among scholars. Despite its decline, the Harappan civilization left a lasting legacy in the form of its urban planning, craftsmanship, and trade networks, which influenced later civilizations in the Indian subcontinent.

In conclusion, the Harappan civilization was an advanced urban civilization that flourished in the Indus River valley. Its well-planned cities, sophisticated trade networks, advanced agriculture, and unique cultural practices make it a significant chapter in human history.