The Lahti City Theatre building is based on the winning entry in an open architectural competition arranged in 1973, won by architect Pekka Salminen and Esko Koivisto. The planning work continued from 1976 to 1983. Construction began in autumn 1980 and the opening night took place in September 1983.

The theatre serves for both straight and musical drama. The possible use of the building for exhibitions, meetings, and congresses was also taken into accounts in planning.

The theatre building includes three auditoriums with a total of 1190 seats. The main material of both the interiors and the facades is concrete worked with various methods.

The plaza, with its patterns made up of grey and red granite paving, forms an important element of the urban structure in front of the theatre. A part of the foyer is a direct continuation of the plaza. Performances of various kinds can also be staged in the foyer and on an outdoor stage in the plaza.

The main objective in planning the foyers was to create an area which could be used actively in daytime. Several small staircases up to the second foyer level have been substituted for the standard monumental stairway. The main stage is used primarily for straight drama, but musicals can also be performed on it. In order to maintain the flexibility required for future changes in the theatre, the entire sides of the stage opening are movable. The maximum number of spectators in the small auditorium is 300.

The stage and auditorium form a single spatial unit. In the principle, the performers should be able to enter a fully convertible stage like this from anywhere. The main auditorium sits 770 spectators.

The third room for public performances is in the basement under the inner courtyard. The room seats 120 spectators and can be used for small scale performances.

The principal designer of the building was Pekka Salminen. During the development of the winning concept, he was assisted by Osmo Honkanen, Juhani Siivola and Jarno Kuurne. Yrjö Kukkapuro and Kimmo Varjoranta designed the seats to the large and small auditorium and the sofas and chairs to the foyer.