What was the name of the Athenian council instituted by Solon that had 400 members?

The Athenian council established by Solon that consisted of 400 members is known as the Boule. This council was crucial in the political restructuring of Athens during the early 6th century BCE, a period marked by significant reforms aimed at alleviating social tensions and increasing civic participation.

The Boule served as a key governing body, overseeing the administration of the city and preparing matters to be presented to the larger assembly of citizens. By including representatives from different tribes, Solon aimed to enhance democratic governance and reduce the concentration of power among the aristocracy. This structure allowed for a broader representation of the populace in the political process, laying foundations for the later development of democracy in Athens.

The other options refer to different Athenian institutions: the Ekklesia was the principal assembly where citizens debated and voted on legislation, the Areopagus was an aristocratic council that handled serious criminal cases and had various powers before reforms reduced its influence, and Heliaia was the people's court that adjudicated legal disputes. Each had its own distinct function in Athenian governance but none were specifically the council instituted by Solon with 400 members.