Text: Hundreds of years ago, in Osaka's heyday as the country's theater and entertainment capital, the biggest stars would arrive by boat to enter the riverside back entrances of the many theaters on Dotomburi, which is just south of the river.
Entailment: In Osaka's heyday were the country's theater and entertainment capital.
Contradiction: In Osaka's heyday was when the country was known for its brilliant use of artwork.