Sainte-Chapelle

Tucked inside a courtyard of old law buildings on the island in the Seine, a plain stone exterior hides one of the most dazzling interiors in Paris: a small Gothic chapel whose upper walls are made almost entirely of stained glass. This is the Sainte-Chapelle, a jewel box of coloured light built for a king.

It was built in the 1240s by King Louis the Ninth, later made a saint, to house precious relics of Christ that he had acquired, including what was believed to be the Crown of Thorns. The chapel was, in effect, a vast reliquary, a shrine in the form of a building.

From outside it is modest, hemmed in by later buildings, so the impact comes when you step inside and climb to the upper chapel. There the walls seem to dissolve into glass, fifteen great windows of deep blue and red rising all around you to a star-painted vault.

The windows tell stories. Across thousands of small panels they show scenes from the Bible, from the creation through to the bringing of the relics to Paris, a whole sacred history in glass, meant to be read by the light pouring through.

The effect depends on the light. On a bright day the chapel glows, the colours falling across the floor and the visitors, and the whole space feels alive. On a grey day it is quieter and darker, so a sunny visit, ideally late morning, is worth aiming for.

The lower chapel, where you enter, is humbler and darker, painted in rich colours and once used by the palace staff, while the dazzling upper chapel was reserved for the king and his close circle. The contrast between the two heightens the surprise of the climb.

The chapel was part of the royal palace on the island, the seat of French kings before the Louvre, and it sits today among the courts of justice that grew up on the same site. Its survival through revolution and time is itself remarkable.

It is small, so a visit need not be long, but the upper chapel rewards lingering, turning slowly to take in the full ring of windows. Many people are surprised by how strongly the space affects them despite its modest size.

Because it is small and popular, it can become crowded, and queues form, partly because of the security checks at the law-court complex around it. Booking ahead and coming early both help you enjoy it with a little more room.

It sits a very short walk from the great cathedral and the other sights of the island, so it folds easily into a day exploring the historic heart of the city, ideally timed for when the sun is on its windows.

A few practical notes. Entry is ticketed, and a combined ticket with the nearby former prison can be good value; expect airport-style security. Choose a bright day and the late morning if you can, for the windows at their best.

Stand in the centre of the upper chapel, turn slowly, and let the coloured light surround you, then remember it was built simply to hold a relic and honour a king's faith. Few small spaces have such a powerful effect. When you step back down into the courtyard, the ordinary daylight seems pale by comparison.