The mysterious map first left experts scratching their heads, but with the help of maritime history shop Fartygsmagasinet in Stockholm, where the map was found, its background has now been established ...

"The rock I’m standing on is old," says my guide, Per-Arne Olsson. “Two billion years old, to be precise.” I’m in Sweden’s second-smallest province, Blekinge, which translates as ‘calm ...