It will soon be Easter weekend in Paris—called Paques in French. While I’m not at all religious, I do have a deep appreciation for the role of Catholicism in the history of Europe (both good and, in some cases, very, very bad), particularly in all of the fine art and architecture that can be seen via Paris’s 125-plus churches.

One of the very best of Paris’s churches—and a must-see destination for all first-time visitors to the City of Light  (and many repeat travelers as well)—is the dazzling Sainte Chapelle, located just a few blocks from its more famous cousin, Notre Dame.

Commissioned by King Louis IX to hold his large collection of religious relics—including what is reported to be the crown of thorns worn by Jesus during his crucifixion and pieces of the “True Cross”—Sainte Chapelle was built between 1239 and 1248, and is considered France’s best surviving example of Rayonnant-Gothic architecture. While now open to the public, the church was initially a private chapel that was part of a sprawling royal place. (That palace today is divided into several buildings, including the church, the Conciergerie—a one-time prison that housed Marie Antoinette, among others, and the French Ministry of Justice.)

The exterior of the chapel is ornate but not extraordinary, and certainly not nearly as grand as nearby Notre Dame with its flying buttresses and intricate carvings. It’s what’s inside that makes Sainte Chapelle unique and breathtaking—the world’s most extensive collection of 13^th century stained glass, more than two-thirds of it still intact after more than 760 years.

Fifteen huge windows (each more than 50 feet high and nearly 14 feet wide) frame the church’s nave and apse, while an enormous rose window is positioned over the entrance to the chapel. In fact, the vast majority of the church’s walls are made up of the stained-glass windows—the thin stone walls serve primarily as a framework and support structure for the windows.

The windows near the apse tell stories from the Bible’s New Testament, primarily of Jesus’s birth and crucifixion, plus the life of John the Evangelist. The windows of the nave are dedicated to Old Testament stories, and actually include a window telling of how the holy relics housed in the church were obtained by Louis IX and brought to Paris.

The “shell” of the church is largely a recreation due to extensive restorations following the French Revolution, which saw significant damage inflicted on the chapel—including the removal of the church’s steeple, altar and religious relics. (The relics can be viewed today at Notre Dame.) But about 70% of the stained glass pieces in the chapel’s windows are original, unbroken and unretouched segments dating from the 13^th century.

When the sun is shining and the chapel is fully illuminated, they are simply breathtaking.

Sainte Chapelle has been a French national historic monument since 1862. Today, the church serves primarily as a tourist destination and the venue for several classical music performances held throughout the year. The last Catholic mass was held at the church in 1892.

Because Sainte Chapelle is part of the Ministry of Justice complex, visitors must enter through only one small entrance, pass through metal detectors and follow a strict path to and from the chapel.

A note to would-be visitors: Because Sainte Chapelle is nestled inside the Ministry of Justice, sunlight is blocked by surrounding buildings early in the morning and in late afternoon (particularly in the winter months). To fully experience the stained-glass windows in all their glory, visit when the sun is significantly above the horizon. The same sort of tip is offered for visiting on gloomy days–of which Paris has many): Cloudless days provide the best views.