La Rochelle continued

With its importance as a port dating back so far, the harbour entrance is well fortified .

On the approach to the tower in the third photo (La Tour de La Lanterne,  used as a prison for Dutch, Spanish and English sailors  between the 17th and 19th centuries , and apparently with interesting graffiti from that time, though we didn't go inside), you can walk along the old walls. It's actually pretty much a street till you get to near the end, with some lovely houses along it.

Rue sur les murs / Road on the walls

I can't help wondering was it always so tidal!! It doesn't seem that such major fortifications would have been necessary if that had always been the case. I'm sure the ferry captains are well used to navigating the narrow channels at low tide, and they were well buoyed, but still...
You can see the modern part of the city to the left in the first photo.