The Opera House was designed by Hyvämäki-Karhunen-Parkkinen architects (1977). The elevations are finished in ceramic tile, render and natural stone, while the public spaces inside combine the lucidity of Carrara marble with the glow of red beech. The great glass wall of the main foyer opens out towards Töölönlahti bay and Hesperia Park. Almost all of the furniture and lighting fixtures were custom-designed for the Opera House.
The Opera House is equipped with modern stage technology measuring up to international standards, enabling high-quality opera and ballet performances and joint productions with opera houses abroad. The main auditorium seats 1,350, while Almi Hall seats 200 to 500, depending on the configuration.
The main stage has an area of 500 m2; the stage tower is 28 m high. The wings and backstage areas are big enough to accommodate the movement of large set components. The stage can be rotated, raised or lowered as the director and set designer require. The stage is divided into four sections, which can be moved independently up and down to create effects in performance or to bring set components up from storage to the stage level.
The orchestra pit can also be raised, lowered and resized according to the size of the orchestra and the acoustic effect required. The stage technology and orchestra pit of the main stage were renovated in 2007 to ensure safety and reliability.
Operas are performed in the original language, as is the international practice. A Finnish, Swedish and English translation is provided as surtitles, i.e. displayed at the top of the stage.