The Cathedral of St. Etienne has a Carolingian altar top that go back to the 10th C.  The cathedral itself is dramatic, if fairly new (by the interests of this page). It was largely constructed in the 13th C. These pictures give a sense of the cathedral and the schematic shows the age of different elements of the church. The red and blue portions are 13th C, green 15th C, and gold 16th C.

The 9th century church was the site of a number of significant Carolingian events. Louis the Pious was re-crowned here as emperor in 835 after the revolt of his sons ended. In 869 Charles the Bald was crowned king of Lotharingia, a title and land claim that did not stick. However, this earlier church gave way to a newer Romanesque church, which in turn was taken town and rebuilt in the gothic style. That's generally what we see today.

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The crypt is 16th century. During the excavations archeologists found a Carolingian altar slab.

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The oldest item in the cathedral treasury is the ring of St. He died in 641, after serving as bishop of Metz from 614 to 629.

St. Pierre aux Nonnains. There are elements of the chancel (?) that are Merovingian in origin and preserved in the Museum of Art and History. (Alsace Lorraine 91, 3rd edition, undated)

Metz is 330 km W of Paris on the A4