Explanation: The direct democracy characteristic of ancient Athens, or else known as Pure Democracy, is one in which literally all citizens participate in decision making and vote on important political decisions. Decisions would be made by majority vote. This meant that all the townspeople would gather in one place, which was the big city squares with especially acoustic amphitheatres, where all the townspeople could express their opinions and everyone else could hear them.
Such a thing is simply not possible in modern democracies because there is no place where all the citizens of one state would gather and discuss politics in the same way as in the Athens' amphitheatres. That's why representative democracies are represented in modern countries today, and decision-making places are parliaments.