The Cathedrale Notre Dame de la Treille takes its name from a 12th-century figure of the Virgin that has been long revered in the city. The cathedral was built by wealthy inhabitants of the city, starting in the late 19th century; building didn't finish until the 1990s! Sadly, the Virgin is no longer inhabiting the cathedral - she was stolen in 1959, and her church now gets by with a replica.
The cathedral features eight chapels in the neo-Gothic style featuring scenes from the lives of Christ, the Virgin and the saints. There's also a towering organ and, unusually, a great deal of 20th-century stained glass, including an asymmetric rose window.
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The cathedral is in the northwest of Lille; it's most easily reached by train.