Complex sentence: The city was founded in the 3th century by Shapur I as a Sassanid satrapy capital.Became the capital of Tahirid dynasty and reformed by Abdullah Tahir in 830, selected first capital of Seljuq dynasty by Tughril in 1037.
Split into simpler sentences: The city was founded in the 3th century by Shapur I as a Sasanian satrapy capital. Nishapur later became the capital of Tahirid dynasty and was reformed by Abdullah Tahir in 830, and was later selected as the capital of Seljuq dynasty by Tughril in 1037.