Complex sentence: Manhattan Construction built the Oklahoma State Capitol, the George Bush Presidential Library, the Cato Institute headquarters, New Orleans Sports Arena, The Ballpark at Arlington, and is building part of the new visitors center at the United States Capitol.
Split into simpler sentences: Manhattan Construction built the Oklahoma State Capitol, the George Bush Presidential Library, the Cato Institute headquarters, New Orleans Sports Arena, and The Ballpark at Arlington. The company is building part of the new visitors center at the United States Capitol.