History: The original Legion HQ was a rocketship "Clubhouse" modeled after the one which brought baby Kal-El to Earth in the 20th century. The three original Legionnaires talked R.J. Brande into adding several improvements to the Clubhouse such as: underground caverns, meeting rooms and providing the best crime-fighting technology that money could buy. It served as the base of operations for the Legion of Super-Heroes until it was destroyed in a battle with the Fatal Five (Adventure Comics #366).
The next Legion HQ was a giant citadel built in Smallville, Metropolis (Adventure Comics #367). The towering edifice has been destroyed and rebuilt many times.