Introduction:
The first traveler to visit Bihar was Megasthenes, an ancient Greek ambassador and historian. He visited Bihar during the reign of Emperor Chandragupta Maurya in the 4th century BCE. His detailed accounts of the Mauryan Empire provide valuable insights into the history, geography, and culture of ancient Bihar.

Explanation:
Megasthenes:
- Megasthenes was a Greek ambassador who visited the court of Chandragupta Maurya in Pataliputra, the capital of the Mauryan Empire, which is now modern-day Patna in Bihar.
- He was sent by Seleucus Nicator, the Greek ruler of the Seleucid Empire, to establish diplomatic and trade relations with the Mauryan Empire.
- Megasthenes spent several years in Pataliputra and closely observed the administration, society, and culture of the Mauryan Empire.
- He documented his observations in his book called "Indika," which is one of the earliest and most detailed accounts of ancient India.

Importance of Megasthenes' Visit:
- Megasthenes' visit to Bihar provides crucial historical evidence about the Mauryan Empire and its capital city, Pataliputra.
- His writings describe the grandeur and opulence of the Mauryan court, the efficient administration, the vast army, and the advanced infrastructure of the empire.
- Megasthenes also provides insights into the society, economy, and culture of ancient Bihar, including information about the caste system, religious practices, agriculture, and trade.

Other Travelers:
- Hiuen Tsang: Hiuen Tsang was a Chinese Buddhist monk who visited India during the 7th century CE. Although he traveled extensively in India and recorded detailed accounts of his journey, there is no evidence to suggest that he specifically visited Bihar.
- Fahyen: Fahyen, also known as Faxian, was another Chinese Buddhist monk who visited India in the 5th century CE. While he did travel to various parts of India, there is no mention of him visiting Bihar.
- Itsing: Itsing, also known as Yijing, was a Chinese Buddhist monk who visited India in the 7th century CE. Like Hiuen Tsang, there is no specific mention of him visiting Bihar.

Conclusion:
In conclusion, Megasthenes was the first traveler to visit Bihar during the Mauryan Empire. His detailed accounts in the book "Indika" provide valuable historical information about the Mauryan Empire and the ancient society of Bihar. While other travelers like Hiuen Tsang, Fahyen, and Itsing also visited India, there is no evidence to suggest that they specifically visited Bihar.