I recently toured the Southwest coast of France and was entranced by the remaining German WW2 bunkers. And in researching them on the web I came across a vast number of resources, in many languages, on WW2 coastal fortifications.
While little survives of the WW2 or WW1 German navies, I started researching the fate of the Gneisenau, sister ship of the Scharnhorst. These two battleships had an odd armament with nine 11 inch guns in three triple turrets; their peers had at worst 14 inch guns or more likely 15 or 16 inch guns. Other than this under caliber on the main turrets they were fine ships and quite effective in their role. In 1942, after their "channel dash", the Gneisenau was hit by air attack and declared a total wreck. The Germans, being efficient scavengers, made full use of all the high caliber weapons and were able to pull two entire turrets into case mates and likely impregnable positions on the Norwegian coastline in separate forts. This excellent web page (highly recommended that you read it) shows the history of this installation and has a color picture of the turret firing to check accuracy after its installation. While there aren't any large caliber German ships preserved (for obvious reasons), this complete turret is very historic and perhaps something I'd make a tour to visit someday.
My interest in coastal artillery comes from many sources but I was always impressed by a book that I picked up as a kid for $1 called "The Guns 1939-45" by Ian V. Hogg. In this book he describes how effective coastal artillery could be, when well sited and protected, against naval attack. This passage, on p131, describes a raid by 5 small Italian naval craft against Malta which had well prepared defenses.
The lights revealed five PT boats in line ahead, racing for the harbor, the nearest being about half a mile from the guns. The twin-sixes (British six inch guns, which would be main armament for a light cruiser or secondary armament on a battleship) and within seconds every boat was hit, three being sunk instantly and the other two disabled and foundering. The remaining boats making up the next wae of the attack turned about and headed for the open seas and their parent vessels, but the twin-sixes... harried them out to maximum range, disabling and damaging most of them.The book, for some reason, didn't cover the original Norwegian defenses that took a heavy toll of the German attackers; as a kid I also remember reading about the sinking of the German heavy cruiser (armed with 8 inch guns) by the Norwegians in 1940; this Wikipedia page describes the coastal defenses and the fact that guns and torpedoes from the early 1900's were able to destroy this modern, expensive and scarce German heavy cruiser (I didn't know until I read this page that Lutzow backed out of range from the fortress full speed astern and had one of her turrets knocked out, too).
In reading other sources on Norwegian coastal fortifications not only did they retain the German guns after Germany's surrender (Norway was never invaded by the Allies) but they also upgraded the guns in the cold war years, when they were on the front line against Russia and the Soviet Bloc. These guns would have made any sort of naval attack very difficult unless they were knocked out in advance or outflanked by infantry.
While I still have that book by Hogg on WW2 guns the internet has been a tremendous boon in researching military topics and following threads on related issues. In the old days I would have had to retain all my books or go to the library or more likely page through a local bookstore but now I can find lots of facts online, with photos as well. A solid way to do research, or more likely just waste some time.
Cross posted at Chicago Boyz