Complex sentence: The pavilion consisted of two components; a exhibit hall that would become the Spokane Convention Center after the fair ended and a 2,700-seat opera house that would eventually become the Spokane Opera House (now known as the INB Performing Arts Center).
Split into simpler sentences: The pavilion consisted of two components; a exhibit hall and a 2,700-seat opera house. The exhibit hall component would become the Spokane Convention Center after the fair ended and the opera house portion of the facility became Spokane Opera House (now known as the INB Performing Arts Center).