Here are found theatres in the overall style of the Ópera, in Paris. Eclectic in design and built in the early years of the 20th century, these buildings represent the triumph of the secular world, and of the hierarchies within bourgeois society. Overflowing with luxury, they transmit the feeling of ostentation and power. The exterior emphasizes their position in the urban environment; there is an excessive load of ornament, and the three spaces corresponding to the principal parts of the theatre: entrance and foyer, hall and stage. The interior is more highly developed, more sumptuous than the preceding group. The hall is horseshoe-shaped and surmounted by a depressed vault. Problems of visibility and acoustics are now addressed. The stage occupies a larger space, and is equipped with accessory areas. Metal structures are used for the flies, so as to avoid the once-common fires. The orchestra is often relegated to a pit, to keep it out of the public view. The use of electricity makes it possible to darken the hall during the performance which, in this type of theatre, is an eminently worldly encounter; thus the bustle of a festive and elegant public in an opulent and colourful environment is even more enticing than the play being performed.