Colt installed a smoke control system with fire / smoke ventilation that met the regulatory requirements, as well as the demanding acoustic requirements set down in the brief The Copenhagen Opera House (in Danish usually called Operaen) is the national opera house of Denmark, and among the most modern opera houses in the world. It is also one of the most expensive opera houses ever built with construction costs well over 500 million U.S. dollars. The Opera House is located on the island of Holmen in central Copenhagen and has six directly connected stages within. Colt designed and provided a smoke control system in this extraordinary building, consisting of Meteor MLS natural flap ventilators, providing a huge 55 dB acoustic attenuation prohibiting external noise from penetrating the building and affecting stage performances.