The Sancta Sanctorum complex. Lighting sacred plac

“Non est in toto sanctior orbe locus” (there is no more sacred place in the world than this) are the words that have stood over the Scala Sancta or Holy Stairs since the sixteenth century. The Sancta Sanctorum (or Holy of Holies) is where the Catholic religion’s most sacred relics are kept. For centuries the place was accessible to a few people only, especially in the early Middle Ages, when it was the Pope’s private oratory in the Lateran Palace in Rome. Because of the many relics that were kept in an arch protected by a massive iron grille, in the ninth century, this area around the ancient shrine dedicated to Saint Lawrence, began to be called the ”Sancta Sanctorum”.

A celebrated icon of Christ the redeemer known as the Acheiropoieton (not made by human hands) is also kept here. The name of the icon comes from the fact that it was supposedly painted by Luke the evangelist and finished by an angel.

Since 1587, the Sancta Sanctorum, located between the Chapels of Saint Silvester and Saint Lawrence, has been reached via the Scala Santa, that was supposedly brought to Rome by Saint Helena, Constantine’s mother, in 326 AD. According to this tradition, these are the stairs that Christ climbed to reach Pontius Pilate’s Praetorium before his crucifixion. On each side of the Scala Santa, there are two additional staircases.

This complex, which Pope Sixtus V (1585 – 1590) enhanced and then entrusted to the specifically established “Sistine College”, which became responsible for its financial administration, therefore has a clear pictorial and architectural value. The college, however, was closed in the mid-19th century and the Stairs were then entrusted to the Congregation of Passionist Fathers in 1853 by Pope Pius IX.

It was these Passionist Fathers, who from the 1990s to the end of the century raised the funds required to carry out this detailed and painstaking restoration. In 2015 iGuzzini joined the project as a technical sponsor. The project has reduced the energy consumption of the lighting system and improved visitors’ perception of the artworks in the complex without altering its mystical atmosphere. This is particularly unique as the Scala Santa can only be climbed by pilgrims on their knees. Believers have demonstrated their faith like this for centuries, as testified by the worn marble steps, which can now be seen as the wooden covers that have protected them since 1723 have currently been removed. Pilgrims can therefore view the original staircase until the Day of Pentecost, which falls this year on the 9th of June. After that the steps will be covered with wood again.

The lighting design for the complex had two main aims: to create a high efficiency system and to improve the chromatic perception of the frescoes. All the devices are LED luminaires equipped with DALI protocol so that special lighting effects and the whole system can be easily controlled.

The luminaires were installed as the various areas were restored. The aim was to create a soft, diffuse, homogeneous lighting effect in all the environments that would allow the frescoes to be seen properly, with no glare, in a clear and transparent atmosphere.

The Chapel of Saint Lawrence and its vaulted, frescoed ceiling was the first area to be illuminated, followed by the rest of the church where religious services are still held. The lighting solution is based on opposing pairs of Palco projectors with high colour rendering and a colour temperature of 3000 K. The direct downlight projectors guarantee the correct degree of lighting during the religious services that are held in the chapel, while a second group of projectors with criss-crossed beams illuminate the ceiling with an even light that avoids uncomfortable peaks of brightness. The altar area is lit by Cestello luminaires, a projector that groups together 3 adjustable lamps individually. Some of these lamps are focused on the altar, others on the tabernacle and others on the area of the faithful.

Palco projectors with high colour rendering have also been installed on the existing cornice in the Chapel of Saint Silvester, on the left side of the Sancta Sanctorum, to illuminate the frescoed ceilings and lunettes. For the Sancta Sanctorum itself, a special system was designed whose main aims were: to make the frescoes at the top of this small space more visible, to improve the rendering of the entire colour range (the previous lighting system featured traditional lamps with colour temperatures that emphasized the warm tones only) and to minimize the visual impact of the actual luminaires as the environment is extremely small. As a result, Laser Blade Tunable White luminaires with a CRI 90 were installed (the same type used at the Scrovegni Chapel) on the splay of the windows. The luminaires are installed in pairs with an uplight emission for lighting the dome and a downlight emission for lighting the strip of frescoes. Under the supervision of Arnold Nesselrath (the then Vatican Museum project manager) Tunable White technology was installed, which allowed a better colour temperature to be selected so the entire colour range of the frescoes can be seen better. The low luminance of the devices also means that the frescoes can be viewed without any visual disturbance.

The lower part of the Sancta Sanctorum with its marble decorations is lit by Underscore Ledstrips thhat have been carefully positioned so they cannot be seen directly by visitors. To light the Acheiropoieton Christ a grazing light effect was created from underneath using a Linealuce luminaire to avoid glare and undesired reflections.

Beside the steps, on the walls which are completely frescoed, Underscore Ledstrip luminaires with a colour temperature of 3000 K and 4000 K have been installed on the cornices and are therefore hidden from sight. This system illuminates the walls vertically with a gradual and even light and the two different colour temperatures have been balanced by the architect Francesco Pezzini, the master restorer Paolo Violini and Father Francesco Guerra, the rector of the sanctuary, to create the most effective temperature for highlighting the entire colour range that includes cold blue and green hues and the warm reds and pinks of the flesh tones.

In the upper transept area, at the end of the steps and on the cross-vaulted ceiling there are frescoes on both the walls and small domes. These have been lit using ultracompact Palco projectors (mounted on a Low Voltage track). Despite their minimal size, the luminaires emit light flows that are intense enough to allow the frescoed walls and domes to be seen clearly. The control system allows each flight of steps to be lit with different intensities.

The lighting system on the Scala Santa, which completed the restoration project consists entirely of Underscore High Power luminaires, which create a uniform wallwasher effect on the vaults and walls. Thanks to their size and position on the cornice, these luminaires are completely invisible to the faithful who can therefore enjoy an experience of devotion with no glare or any visual disturbance of any kind. The overall project has therefore given this sacred complex back to pilgrims and the citizens of Rome who can now fully enjoy its architectural, pictorial and devotional values while also saving energy.