Join Jersey War Tours and visit WW2 bunkers, which are not usually open to the public.
JWT will show you how Jersey was made into an impregnable fortress and help you appreciate what the Third Reich was able to create with slave labour.
The tour is also a perfect complement to understanding the history of the D-Day invasion, which took place less than 30 miles away.
£35pp or you can go private for £175 for up to 7 people (just select the “book entire tour option”).