In ancient Greece, a place where athletes exercised in the nude.  Every important city had a gymnasium.  By the Hellenistic era, the gymnasium usually included exercise apparatus and equipment, bath [..]

1590s, "place of exercise," from Latin gymnasium "school for gymnastics," from Greek gymnasion "public place where athletic exercises are practiced; gymnastics school," i [..]

There is no equivalent in English. Explain that this is a form of pre-university education, comparable to English grammar schools, that includes the study of Latin and/or Greek.

Gymnasium derives from the Greek gumnos, (meaning naked). It was a place where people exercised naked. The modern word gym derives from gymnasium.Example 1: Gymnasiums and sanctuaries

a large room fitted with ropes, bars and all kinds of equipment for exercise

Greek for a place where you train naked.

(n) a school for students intermediate between elementary school and college; usually grades 9 to 12(n) athletic facility equipped for sports or physical training

N sports centre

Workout room with weights, and a range of cardio and variable resitance equipment. 

grammar school (''UK''), prep school (''US'') (''a school used to prepare students for university'')