Kong Bai Stadium is an outdoor arena presumably used for large significant events. It was featured in the Kung Fu Panda: Legends of Awesomeness episode "Has-been Hero" where Po describes his earliest memory of Kwan in the stadium.
Much like the Bao Gu Orphanage, the stadium is a large circular building. The exterior features a bare wall with a single ring of windows and flags lining the roof. The interior houses the stage where wrestlers compete, with the crowd watching from the hundreds of seats surrounding the stage.
In "Has-been Hero", while heading through the village, Po spotted a poster advertising the return of Kwan the Unkillable. Excited, Po had a flashback of the last time he had seen Kwan in action: in Kong Bai Stadium, a young Po sat with a variety of snacks as he watched Kwan face his latest opponent. After beating down his opponent, Kwan prepared to make the final blow: a new move he was planning to introduce called the "Ram Slam".
What Po didn't know was that during that day, he had unintentionally made Kwan lose the match: during the fight, Kwan caused a shockwave that spread through the stadium and made one of Po's dumplings fly into the air. That dumpling hit Kwan right in the eye in the middle of the Ram Slam, sending him crashing to the ground and humiliating him in front of the entire crowd. As a result of this incident, Kwan lost every match afterwards, ultimately wrecking his career.