Basilica of Sant'Apollinare Nuovo

Step inside and let your eyes adjust. The light here is soft and grey at first, falling through the windows high above the nave. Then the walls begin to glow. Gold, white, deep green and blue rise on either side of you, row after row, all the way up to the roof. Listen for the quiet shuffle of feet on the stone floor, and the low murmur of people who have just looked up at the same moment you did.

You are standing in a church built about fifteen hundred years ago, in the early sixth century. Its builder was Theodoric, a king of the Ostrogoths, a Germanic people who ruled Italy after the fall of the Western Roman Empire. Theodoric made Ravenna his capital. He built his palace nearby, and this basilica served as his palace church. It is one of the reasons Ravenna is often called a city of mosaics.

Here is the first surprise. This church was not built for the kind of Christianity that later took it over. Theodoric and his Goths were Arian Christians. Arianism was a branch of early Christianity that saw Christ as created by God the Father, not equal to him. The Roman population of Ravenna, and the bishops of Rome and Constantinople, saw this belief as heresy. So for its first decades, this building was a church of the ruling minority.

That changed after Theodoric's death. In the mid sixth century, armies of the Byzantine emperor Justinian took Ravenna back for the Eastern Roman Empire. The church was handed to orthodox Catholic worship. It was rededicated to Saint Martin of Tours, a saint known for fighting heresy. For a time, people called it San Martino in Ciel d'Oro, which means Saint Martin in the Golden Sky. Look up at the walls and you will understand the name.

The mosaics on the long walls run in three horizontal bands. At the very top, small panels show scenes from the life of Christ. On the left wall, as you face the altar, you see his miracles and parables. On the right wall, you see his Passion, the events leading to his death. Look closely at his face. On one side Christ appears young and beardless. On the other he is older and bearded.

Below those scenes, in the spaces between the windows, stand tall single figures in white robes. They are usually identified as prophets, saints or apostles. They hold books and scrolls, and they stand quietly, almost like a second congregation looking down at yours. Many visitors never notice this middle band at all, because the lowest band pulls the eye so strongly.

That lowest band is the great procession. On the left wall, a long line of women in jewelled robes walks toward the Virgin Mary, who sits with the Christ Child on her lap. These are the virgin martyrs, women honoured by the early Church for dying for their faith. They leave from a city by the sea, shown near the entrance. That city is Classe, Ravenna's ancient port. Look for the ships in its harbour.

Just ahead of the women, three men in bright, patterned clothing hurry forward with gifts. They are the Magi, the wise men from the Christmas story. They wear short tunics, trousers and red Phrygian caps, the soft pointed hats Romans linked with the peoples of the East. Above their heads you can read their names in the mosaic: Balthassar, Melchior and Gaspar. These names are now familiar across the world, and this is one of the earliest places where you can see them written.

Now turn to the right wall. Here a line of male martyrs walks toward Christ, who sits on a throne between angels. Leading them is Saint Martin, the saint to whom the church was rededicated. Many scholars believe both processions were changed after the Byzantine takeover. The original Arian figures, perhaps including Theodoric and his court, were likely replaced by these rows of saints. The church kept its gold, but changed its message.

Near the entrance on this right wall is the most famous detail of all. You see a building with arches and the word Palatium, meaning palace. This is Theodoric's palace. Between its arches hang white curtains. But look at the columns. Here and there you can still see the edges of hands, pressed against the stone. Figures once stood in those arches. They were removed and covered with curtains, but a few fingers stayed behind. It is a fifteen-hundred-year-old act of political erasure, and it is still visible.

The church takes its present name from a later chapter. In the ninth century, the relics of Saint Apollinaris, the first bishop of Ravenna, were brought here from his basilica at Classe. According to the usual account, they were moved to protect them from raids along the coast. So the building became Sant'Apollinare Nuovo, the new Saint Apollinaris, to tell it apart from the older church at Classe.

Before you leave, look at the structure itself. Two rows of marble columns carry the walls, with carved capitals at the top. The floor today sits higher than the original one, because the ground level of Ravenna has risen over the centuries. Outside, you will see a round brick bell tower, added long after the church was first built. In 1996, this basilica joined other early Christian monuments of Ravenna on the UNESCO World Heritage List.

Take one last slow walk down the nave. Let the women on your left and the men on your right walk beside you toward the altar, as they have for centuries. When you step back outside, the brick walls look plain, almost modest. That is part of the experience here. The gold is all inside. As you walk away, think of those few hands on the palace columns, still holding on.