A Monumental Makeover in the Eternal City

This summer, the mayor of Rome, Walter Veltroni, inaugurated a new lighting system for one of the Eternal City's most famous monuments — the Colosseum.

Designed to hold 50,000 spectators, the building was begun by Emperor Vespasian, inaugurated by Titus in 80AD, and completed by Domitian. The first permanent amphitheatre to be built in Rome, its monumental size and grandeur, as well as its efficient organization for producing spectacles and controlling crowds, make it one of the Roman Empire's great architectural achievements. The amphitheatre is a vast ellipse measuring 188m by 156m (615'×510'), with a base of about six acres. Vaults span between radial walls to support tiers of seating, passageways and stairs. The facade of three tiers of arches and an attic level is about 48.5m (158') tall — equivalent to a modern 12- or 15-story building.

Approximately 80 entrances facilitated the crowds' entry and exit. Below the wooden arena floor was a complex of rooms and passages which held wild beasts and other material for staging spectacles. At the outer edge, circumferential arcades link each level and the stairways between levels. The three tiers of arcades are faced by three-quarter columns and entablatures: Doric on the first level, Ionic on the second, and Corinthian on the third. The attic level has Corinthian pilasters and small square window openings that once alternated with bronze plaques (unfortunately lost through the centuries). The construction utilized a carefully chosen combination of materials: concrete foundations, travertine for piers and arcades, tuff infill between piers for the walls of the lower two levels, and brick-faced concrete for the upper levels and most of the vaults.

The new lighting project (in collaboration with the Rome Town Council) is the first joint venture by Rome-based multi-utility group ACEA and Electrabel, the leading electricity producer in Benelux, positioned as a global custom-energy solutions provider, with power plants in several countries with a total generating capacity of 25,000MW. The project was drawn up in coordination with the government archaeological office and the approval of the ministry of cultural property. It is an upgrade of an existing system that partially illuminated the monument.

The oldest part of the lighting system comprised 310 Fivep Area P1 CV-L wide-beam floodlights with 70W Osram high-pressure sodium lamps. These lightweight alloy fusion units (now discontinued) were chosen for their high resistance to corrosion and IP55 protection: on ground-floor level, one is installed just inside the arches and another in the passageway behind, giving depth to the internal lighting. On the first and second floors, on the other hand, each arch has a single Area fixture, mounted on the inside stringcourse (the horizontal band of masonry running around the facade of the building) below the interior curve of the arch which it uplights.

Twenty-five pole-mounted Bega 8374 wide-beam symmetric floodlights were already placed on lampposts located on the opposite side of the road running round the entire perimeter of the building. These units, fitted with 400W Philips metal-halide lamps (4000K), are alternated with 15 pole-mounted medium-beam Bega 8393 floodlights with Philips 250W (19,000 lumen) metal-halide lamps. To achieve optimum corrosion-resistance, all the Bega units' aluminum components are chromatized, powder-coated, and painted with special enamel.

Another significant part of the lighting package consists of 38 Schréder RS floodlights fitted with Philips HPI-T 2,000W lamps mounted just inside the third story's supporting arches, pointing outwards and positioned in such a way as to give a “rising sun” effect. These units, installed in every second arch around the entire circumference, are switched on every time a death penalty is suspended anywhere in the world.

The project for upgrading the ordinary lighting (on from dusk to dawn) involves the second, third, and attic levels.

The system was designed by ACEA's Unità Operativa Progettazione di Illuminazione Pubblica, led by Remo Guerrini, who says, “Our aim was to highlight all the monument's architectural features to the utmost, caressing the structure by putting the accent on the key elements, rather than dazzling the millions of tourists who flock to see it every year. The brief was therefore to emphasize the vertical architectural elements on the high part of the building, where the attic level is still standing — in other words, the torus molding and column which characterize each level's layout. The project integrates the previous setup, which concentrated on highlighting the design of the arches and their brickwork, and is fundamental for the monument to be correctly viewed and understood, precisely by emphasizing the parts in travertine stone and the structure's vertical lines.”

This result was achieved using 212 Corus compact tilting floodlights, also by Belgium-based Schréder Group, technical sponsor of the new Colosseum lighting system. The Corus fixtures, fitted with Philips CDM lamps, are installed on the three external stringcourses and focused on the columns on the second, third, and attic levels. On the second and third levels, they are fitted with 35W lamps with a color temperature of 3000K, and, on the attic-level, 70W lamps with the same color temperature. The fixtures, installed in the tilting version for utmost positioning flexibility, were chosen after a survey of outdoor lighting instruments, bearing in mind the building's morphological complexity. They are equipped with asymmetric reflectors, so that the light covers both the columns and the horizontal areas between the arches. The units' extremely low profile (just 9cm, or 3.6") was also a key factor, as it enables them to remain unseen by visitors. Guerrini says, “To avoid excessively powerful lighting levels at the instruments' maximum emission point, they were ordered with medium-grained glass, to ensure softer light diffusion. All the Corus units have asymmetric light distribution with the lamp off-center thanks to the 1653 reflectors chosen for the project: on the second and third levels, the fixtures have been installed with emission focus and asymmetry towards the columns, whereas on the attic level positioning is tangent to the surface.”

The fixtures were installed using a steel cord running between the units and fixed to the monument using lead-covered steel hardware fitted in the wall cavities. Power cables and distro boxes connecting individual fixtures' cables to the main power supply are also attached to this cord, avoiding the need for drilling and allowing easy removal of the lighting for renovation work, which on such important monuments can be required frequently.

Guerrini concludes, “This setup enabled us to achieve the objectives agreed on with the government bodies involved, and the use of these fixtures allowed us to efficiently control the illumination, which almost entirely addresses the required areas and doesn't spill skywards, in compliance with the law regarding lighting pollution. The complete system now includes a total of 600 fixtures and highlights parts of the building hitherto almost unseen at night, while keeping consumption at acceptable levels — in fact, the entire monument's illumination consumes an average of 350kWh per day.”

Mike Clark is an Italy-based UK journalist and can be contacted at mclark@rimini.com.