Santo Spirito, Florence

Stand in the square for a moment and listen. Pigeons scatter across the stone. A café pulls down its metal shutter. Somewhere a bicycle rattles over the paving. In front of you rises a flat, pale facade, almost blank, with a soft curving outline against the sky. It looks unfinished. In a way, it is. This is the Basilica of Santo Spirito, and its plain face hides one of the purest interiors of the Florentine Renaissance.

You are in the Oltrarno, which simply means "beyond the Arno." This is the south bank of the river, away from the cathedral and the crowded heart of the old city. For centuries this was the district of craftsmen: woodworkers, gilders, leather workers, picture framers. Many small workshops still open onto these streets. The square in front of the church is the living room of the neighbourhood. People drink coffee here in the morning, and they gather here again late at night.

The church belongs to the Augustinian friars, a religious order that has been on this site since the Middle Ages. An older church stood here first. In 1471, during a religious festival with a theatrical performance, that earlier building caught fire and was badly damaged. By then, however, a new church was already rising. Its design came from Filippo Brunelleschi — the same architect who built the great dome of Florence Cathedral, across the river.

Brunelleschi worked on the plans for Santo Spirito in the first half of the fifteenth century. Construction began in the 1440s, but he died only a couple of years later, in 1446. Other builders carried the project on for decades. They kept much of his vision, but they also changed parts of it. So the building you see is Brunelleschi's idea, completed by other hands. Some of his intentions survive only in old descriptions.

Here is the first surprise. Brunelleschi reportedly wanted the church turned the other way — facing the river, with a large open space reaching down to the water. That plan was never carried out, partly because of the cost of clearing the land. He is also said to have wanted four doors in the front, not three. The builders chose three. The facade itself was never given marble cladding. It received its simple plaster finish much later, and it has stayed plain ever since.

Now step inside, if the church is open. Let your eyes adjust to the softer light. You will see long rows of columns made from pietra serena, a grey sandstone from the hills around Florence. The grey stone stands against white plaster walls. This combination of grey and white is the signature of Florentine Renaissance architecture. Here it reaches a calm and even rhythm that few buildings match.

Notice how everything repeats. The columns carry round arches. The arches lead to side chapels. The side chapels form a ring that runs along the walls and around the transepts — the arms of the cross-shaped plan. Brunelleschi built the whole space from simple proportions, so the parts relate to one another like notes in a scale. Walk slowly down the nave and feel how regular it is. Very little in the space feels accidental.

The second surprise is outside, and you cannot see it at all. Brunelleschi designed the chapels as curved niches, and he seems to have wanted those curves to show on the outside of the building. Imagine the walls rippling in a row of half-circles. The later builders enclosed them inside a straight wall. So the smooth, flat exterior hides that curving design. Inside, you still feel the curve every time you look into a chapel.

At the centre of the church stands a large high altar under a canopy, added in the seventeenth century. It is richly decorated, in the more theatrical Baroque style that came long after Brunelleschi. Many visitors find it a strong contrast with the quiet stone around it. Look at it and then look back at the columns. You can see two different ideas of what a sacred space should feel like, side by side under one roof.

The side chapels hold paintings that Florentine families commissioned for their own chapels. One of the best known is an altarpiece by Filippino Lippi, showing the Madonna and Child with saints and the family who paid for it. Look carefully at the background. Through an opening in the painting you can glimpse a small view of the city. Other chapels hold works by Florentine painters of the fifteenth and sixteenth centuries, often in their original settings.

Off one side of the church is the sacristy, designed by Giuliano da Sangallo late in the fifteenth century. It is an eight-sided room under a dome, approached through an elegant vestibule with a coffered ceiling. Today the sacristy holds a wooden crucifix attributed to the young Michelangelo. The story goes that the friars let him study the bodies of the dead in the convent's hospital. In return, he carved this figure of Christ. The slender, almost fragile body looks very different from his later muscular figures.

When you come back out, take time in the square. On many mornings there is a small market with fruit, vegetables, and household goods. The fountain and the trees give shade in summer. Next door to the church is the Cenacolo, the old refectory of the convent, where the friars once ate. It now holds a small collection, including a large fragment of a fourteenth-century fresco. Look up at the bell tower, too. It was added in the early sixteenth century, and it rises above the roofs of the quarter.

Before you leave, look once more at that plain facade. It does not try to impress you from the outside. All the effort went into the inside, into the light, the grey stone, and the proportions. Listen to the square again — the voices, the cups, the bicycles. This church has stood at the centre of this neighbourhood for more than five centuries. As you walk away into the narrow streets, watch for the workshop doors still standing open.