The Monument of the Eponymous Heroes
Here were statues of the ten heroes whose names were given to the ten new tribes founded by Cleisthenes in 508/7 BC. These tribes were the basis of the democracy, and provided 10 regiments, elected a strategos (general) to lead each one, and provided 50 members annually for the boule, and feasted together at tribal sacrifices. Members of a tribe came from the three geographical regions - the city, the coast, inland - and, by fighting, feasting and serving as citzens together, bonds of loyalty were forged which were a crucial feature of the democracy.
The monument to the ten heroes after which the tribes were named was also a notice-board: under each statue relevant notices for each tribe would be hung. General information was also posted here - motions for discussion in the ekklesia for example. Citizens would have to visit the monument every day, and it provided an essential focal point.