The cathedral houses 14th-century astronomical clocks, among the oldest in the world.
Adjacent to the cathedral is the "archaeological garden" with the remains of two other 11th-century churches (Saint Stephen and the Holy Cross), destroyed during the French Revolution, as well as excavations of an early Christian baptistery from the 4th century.
This magnificent structure began to be erected during the Merovingian era on the ruins of a 6th-century church; the lower part dates back to 1165–1180. The internal length of the building is 80 meters. Then, over several centuries, as is customary, the cathedral was gradually completed, increasing in size. The main facade dates back to the 14th century, although work on it began a century earlier. Its construction used stones from ancient Roman buildings that once stood on the same site and were destroyed around the 9th century.
Due to such a lengthy construction period, the architectural style of the cathedral is heterogeneous: the oldest part of the building, which faces the Saône River, is Romanesque, while the eastern, most recent part, with the main facade, is Gothic. Attached to the cathedral is the building of the church choir school from the 11th century, which today houses the cathedral treasury museum. In the latter, one can see items from the Byzantine era collected in the 19th century: jewelry, church vestments, tapestries, etc.
In 1245, the cathedral was the venue for the First Council of Lyon.
In the second half of the 16th century, during the religious wars, the cathedral was plundered by Protestants, but later restored. The church also suffered during the revolution, and only in the first half of the 20th century were its choirs restored to their former state.
In 1600, the wedding of Henry of Navarre to his second wife, Marie de' Medici, took place in the Lyon cathedral, and in 1622, the famous Richelieu was elevated to the cardinalate there.
Each December, Lyon celebrates the annual Festival of Lights, a tradition dating back to 1643, when people would place a lit candle in their window on December 8. To this day, many residents still observe this custom. During the festival, the façade of the cathedral features a choreographed lighting display.
The dimensions of the building are 80 meters in length (internally), 20 meters in width at the choir, and 32.5 meters in height in the nave.
The oldest parts of the cathedral, located closer to the water, include the transept, the lower part of the apse, and the side chapels in the Romanesque style. The closer to the facade of the church, the more pronounced the influence of Gothic becomes. The finishing of the three portals, decorated with pointed arches and quatrefoils characteristic of Gothic, was finally completed in 1480. At the lower part of the facade, 320 sculptural medallions are well preserved, depicting fieldwork and zodiac signs. Among the scenes from medieval life captured on them are some very interesting episodes.
Inside the cathedral, there are several details that deserve a thorough inspection. These include the preserved medieval stained glass windows (the oldest dating back to the end of the 12th century), the 15th-century Bourbon chapel with its exquisite sculptures, a statue of John the Baptist created by Blaise in 1780. Two crosses to the right and left of the altar have been preserved from the cathedral of 1274 as a symbol of the union of the churches.
The astronomical clock that can be seen in the Saint-Jean Cathedral is the oldest in the country. The original construction dates back to the 14th century, although after the Huguenot Wars, the clock required restoration in the 16th century. In the following century, the clock's appearance acquired distinctive Baroque features, and in the 18th century, a minute dial was added. Parts of the clock mechanism from the 16th century are still present to this day.
The cathedral's organ, built by Daublaine and Callinet in 1841, initially had 15 stops and was located at the end of the apse. In 1875, it was reconstructed by Merklin-Schütze and given 30 stops, three keyboards with 54 notes, and pedals with 27 notes.