Once one of France's most sacred sites, this basilica was built atop the tomb of St Denis, the 3rd-century martyr and alleged first bishop of Paris who was beheaded by Roman priests. By the 6th century it had become the royal necropolis. Almost all of France’s kings and queens from Dagobert I (r 629–39) to Louis XVIII (r 1814–24) are buried here, including Louis XVI and Marie Antoinette (42 kings and 32 queens in total).
The single-towered basilica, begun around 1136, was the first major structure in France to be built in the Gothic style, serving as a model for other 12th-century French cathedrals. Features illustrating the transition from Romanesque to Gothic can be seen in the choir and double ambulatory, which are adorned with a number of 12th-century stained-glass windows.
The tombs in the crypt are Europe’s largest collection of funerary art and the real reason to make the trip out here. Adorned with gisants (recumbent figures), those made after 1285 were carved from death masks and are thus fairly lifelike; earlier sculptures are depictions of how rulers might have looked.
An audioguide costs €3.
Note that the metro line splits in two at La Fourche, so be sure to board a metro bound for St-Denis-Université.