From the internet journalist:

^{(Image credit: Luc Doudet)}

The Chêne-Chapelle (Chapel-Oak) of Allouville-Bellefosse is the most famous tree in France – actually, it’s more than just a tree: it’s a building and a religious monument all in one.

In 1669, l’Abbe du Detroit and du Cerceau decided to build a chapel in (at that time) a 500 years old or so oak (Quercus robur) tree made hollow by a lightning bolt. The priests built a small altar to the Virgin Mary. Later on, a second chapel and a staircase were added.

Now, parts of the tree are dead, the crown keeps becoming smaller and smaller every year, and parts of the tree’s bark, which fell off due to old age, are covered by protective oak shingles. Poles and cables support the aging tree, which in fact, may not live much longer. As a symbol, however, it seems that the Chapel-Oak of Allouville-Bellefosse may live on forever.

[source]