On the way back from Brittany we visited the garden at Kerdalo. It is a botanists' garden, taking full advantage of the mild climate of the North Brittany coast, and was started by its new owners some 45 years ago. The 25 acres of gardens are constructed along the valley of a small stream that flows into the river opposite Tréguier, and exploits the shelter, the acid soil and the water.
I found fascinating, the trompe l'oeil pathway that leads up to a little grotto, situated right at the bottom of the garden. The stepping stones along the path in the water look like they are the same size, and the channel edges look parallel, but they are not: the path is about twice as wide at the far end than the near.
You really must visit this garden if you are in the area and like plants. Actually it's worth quite a detour. A French guy asked us on the way out if it was worth the entrance fee. "Yes" I was able to reassure him, "it's in the English style".