There's a lot of these! https://en.wikipedia.org/wiki/List_of_bastion_forts https://en.wikipedia.org/wiki/List_of_bastion_forts They're particularly dense in

There's a lot of these! https://en.wikipedia.org/wiki/List_of_bastion_forts https://en.wikipedia.org/wiki/List_of_bastion_forts They're particularly dense in the Netherlands for some reason (had to be broken out per province). There's a bunch along the US East Coast too. I even visited one (on Governors island, New York https://en.wikipedia.org/wiki/Fort_Jay https://en.wikipedia.org/wiki/Fort_Jay ) Now that part still makes sense to me, since the east coast was colonized in the 1700s-ish. What surprised me is that apparently there's a few forts very far inland!