The Millennium Center has a total of 140,000 sq.m. unfolded built-up area developed in 32 floors. It consists of three towers - a hotel on 32 floors, a residential building on 18 floors and an office center on 24 floors, united by a five-floor base. The basement is on 5 levels and contains warehouses, service and technical rooms and parking for 560 cars. The building has 25,000 square meters of Class A business premises, retail outlets, a bank and insurance office on the ground floor, a restaurant, a snack bar, a car care center and service rooms.
The chosen architectural approach - a combination of three buildings reduces the monolithic volume, bringing the scale closer to the urban environment and maintaining a significant presence. The type and colors of the finishing materials are also consistent with the colors and character of the city in order to get as close as possible to the city silhouette. The glass facade reflects the surrounding buildings and the sky, while the grayish color of the facade elements draws a parallel to the building’s surroundings - the National Palace of Culture, the Medical Academy of Sofia and others. This method creates a visual accent while also softening the effect of dominance in the silhouette of the city.
The basement is on 5 levels and contains warehouses, service and technical rooms and parking for 560 cars. The fifth above-ground level is designed as a congress center, occupying an area of 5,300 square meters and containing 6 meeting rooms. The main conference hall has an area of 780 sq.m. and contains seats for 768 people.
The roof structure is designed with a pressure arch and tensioner and is a unique solution for buildings, as it is usually used in bridge construction. It also serves as the roof of the restaurant, located on the upper level. A helicopter pad with a diameter of 22 m has been designed on the roof for landing helicopters with a total mass of 5 tons. It is also calculated for emergency landing with a speed of 3.6 m/s. Below the helicopter pad is located a space for visitors with a stunning view of Sofia in all directions, where the visitors are able to observe the sights of the city.
The structure is monolithic, skeletal and beamless. The seismic load is taken over by central reinforced concrete cores and reinforced concrete frames. The excavation is strengthened by 500 secant piles f600. The foundation of the building has 520 hanging piles with a length of 18 m and a diameter of 1180 mm, while the common foundation slab is 180 cm thick.
The facade is elemental, manufactured by Raynars. The windows are "Glaverbel" - triple glazing - 10.16.4.16.4 with low iron content, which provide 73% reduction of sunlight and six times lower heat transfer through the latest generation coating. Through this combination a sound insulation equal to a wall of 45 cm brick is achieved.
A new generation energy-efficient energy system has been designed for the entire building through an integrated system with intelligent central control.