Last Sunday I showed you a photo of the altarpiece of the Aachener Dom, and mentioned that the shrine containing the remains of Charlemagne was somewhere behind that altarpiece.

Here then, for the Fifth Sunday of Lent, is a view of the area behind the altar, and in the far distance of this photo, beneath the stained glass windows, is the Karlsschrein.

For today, the Fourth Sunday of Lent, I’m posting a photo of the magnificent Palo D’oro of the Aachener Dom, which is believed to date from 1020. Palo D’oro means golden altarpiece.

Behind the altarpiece is the Marienschrein (Shrine of Mary), which holds the four relics that make the Aachener Dom a place of pilgrimage. And behind that, not visible in my photo, is the Karlsschrein (Shrine of Charlemagne) containing the remains of Charlemagne.

Charlemagne is what you call a Big Deal for students of European history. In 768, he became king of the Franks (who lived in northern France and the German Rhineland). In 774, he became king of the Lombards (a Germanic people on the Italian peninsula). And in 800, he was crowned Holy Roman Emperor by Pope Leo III. All that is why Charlemagne is given credit for uniting Western Europe.

Charlemagne is also credited with bringing about the Carolingian renaissance, even though he himself was barely literate. Libraries and schools were established, and Charlemagne invited scholars from England, Germany, France, Italy, and Spain to study at Aachen. A new and simplified system of writing, known as the Carolingian miniscule, came into use. And he created a new currency system based on a pound of silver divided into 20 parts, which were further divided into 12 parts, for a total of 240. This three-part currency was used for many centuries throughout Western Europe. Ireland and the United Kingdom were the last to drop it when they converted to the decimal system in 1971.

For the Third Sunday of Lent, I’m posting a photo of the Barbarossa Chandelier that hangs in Aachener Dom. Four metres in diameter and suspended four metres from the ground, this magnificent chandelier holds 48 candles. It was commissioned by Frederick I, also known as Frederick Barbarossa, who was Holy Roman Emperor from 1155 to 1190.

What sets the Aachener Dom apart from other cathedrals — and what you notice as soon as you step inside — is its shape. Unlike most cathedrals, it’s built in the shape of an octagon, not a cross. Charlemagne is said to have placed a lot of significance on the number 8. Four is another significant number in the Christian faith and, if you’re mathematically inclined, you know that an octagon can be formed by laying one square on top of another after rotating it a quarter turn, and then lopping off the protruding triangles.

For the Second Sunday of Lent, here is a photo of the ceiling of the Aachener Dom, in which the eight sides of the octagon are clearly visible.

When I wrote about Aachen after my summer in Amsterdam some years back, I promised myself I would one day write about its magnificent cathedral.

Today is that day.

The Aachener Dom (Aachen Cathedral) started out as a chapel in the palace of Charlemagne way back at the end of the eighth century. It later became the coronation church of the German monarchs, with 31 kings and 12 queens having been crowned here between 936 and 1531. And Charlemagne himself was buried here; it was the Charlemagne connection that made the cathedral one of the most significant pilgrimage sites during the Middle Ages, along with Rome, Jerusalem, and Santiago de Compostela.

This year’s Lenten series will focus on the Aachener Dom, which is one of the most remarkable churches I have ever visited. For today, the First Sunday of Lent, I’m posting a photo of the only bit of the cathedral I saw from the outside. It’s pretty low key from this side, and belies how spectacular the interior is.

Which is why I was speechless after stepping inside.