The National Technical University of Athens, known as the Polytechnic, keeps one gate permanently locked. It opens just once a year, on November 17, to mark the 1973 student uprising that helped topple Greece's military dictatorship.

For three days in November 1973, students barricaded themselves inside the campus and broadcast calls for solidarity from a pirate radio station. On the evening of the 17th, a tank smashed through the main gate. 23 people died that night, students and members of the public alike.

Founded in 1837, the Polytechnic houses the Art School and several engineering schools, making it one of Greece's most prestigious universities. But it's the annual commemorations that define the place. Schools and universities across Athens shut down for the November 17 march, and riots often break out as crowds gather to remember the resistance.

VoiceMap's self-guided audio tours use the Polytechnic to trace how student resistance became a catalyst for democratic change, connecting the locked gate and pirate radio broadcasts to broader patterns of protest in Athens during the dictatorship years.