Ujjain

City · c. 600 BCE – c. 405 CE · in South Asia

Capital of Janapada of Avanti (600 BCE–405 BCE), Western Satraps (43–405).

Mathura (c. 600 BCE): Capital of Janapada of Surasena (600 BCE–405 BCE).
Milan (600 BCE): Capital of Duchy of Milan (1402–1539), Ambrosian Republic (1450–1450), Cisalpine Republic (1797–1799).
Varanasi (c. 600 BCE): Capital of Janapada of Kasi (600 BCE–451 BCE).
Kushinagar (c. 600 BCE): Capital of Janapada of Malla (600 BCE–451 BCE).
Kausambi (c. 600 BCE): Capital of Janapada of Vatsa (600 BCE–451 BCE).
Vaishali (c. 600–481 BCE): Capital of Janapada of Vajji (600 BCE–481 BCE).
Shravasti (c. 600–501 BCE): Capital of Janapada of Kosala (600 BCE–501 BCE).
Rajgir (c. 600 BCE): Capital of Janapada of Magadha (600 BCE–501 BCE), Magadha - Shaishunaga dynasty (404 BCE–345 BCE).
Viratnagar (c. 600 BCE): Capital of Janapada of Matsya (600 BCE–405 BCE).
Champapuri (c. 600 BCE): Capital of Janapada of Anga (600 BCE–501 BCE).

Around the same time and place

Gautama Buddha (c. 563 BCE – 483 BCE): Founder of Buddhism, born at Lumbini in present-day Nepal. His traditional dates are c. 563–483 BCE; many scholars place his death around 400 BCE.
The Buddha’s enlightenment (c. 528 BCE): According to tradition, Siddhartha Gautama attained enlightenment under the Bodhi tree at Bodh Gaya, the founding moment of Buddhism.
Maurya Empire founded (c. 322–185 BCE): Chandragupta Maurya seized Magadha around 322 BCE and founded the Maurya Empire, the first to unite most of the Indian subcontinent; it lasted until about 185 BCE.
Ashoka (c. 304 BCE – 232 BCE): Maurya emperor who, after the bloody Kalinga War, embraced Buddhism and promoted non-violence and dharma through inscribed edicts across his empire.
Indian numerals (c. 500 CE): Indian mathematicians developed decimal positional notation with nine digits and a zero; transmitted through the Islamic world, it became the numeral system used worldwide.
Zero as a number (628 CE): In his Brahmasphutasiddhanta of 628, Brahmagupta treated zero as a number in its own right and set out rules for calculating with it.
Mahavira (c. 599 BCE – 527 BCE): The 24th Tirthankara of Jainism, who systematised Jain teaching in the Ganges plain. Traditional dates are 599–527 BCE; some scholars place him a century later.
Mahabharata (c. 400 BCE): Vast Sanskrit epic, including the Bhagavad Gita, centred on a war at Kurukshetra. It was composed roughly between the 4th century BCE and the 4th century CE.