What is an outdoor Theatre called?

An outdoor theater with a semi-circular, fan-shaped, or elongated auditorium facing a grass, masonry, or wooden stage. The historic amphitheater took its name from the Greek amphi, referring to the seating “around” or “on both sides” of a performance space.

What is the largest amphitheater in the world?

Colosseum of Rome

The Flavian amphitheatre or Colosseum of Rome, Italy, completed in AD 80, covers 2 ha (5 acres) and has a capacity of 87,000. It has a maximum length of 187 m (612 ft) and a maximum width of 157 m (515 ft).