REMOVE

1. city walls
2. 16th century

WHAT

1. architecture (object genr … (3)
2. city gates (1)

WHERE

1. China (nation) (3)
2. Xi'an, China (3)

WHO

1. unknown Ming (3)

WHEN

1. 14th century (3)
2. 15th century (3)
3. Ming (3)