I had no idea that the Vasa Museum existed until we were in Stockholm. I am extremely glad TL did some research and decided we should go. It's one of my most favorite museums I have ever been to.
Here's the basics, but do more research before you visit... The Vasa sailed off from Stockholm after being hand made by many in 1628. 20 minutes after it began its voyage, it sank. Because the water is so cold, the ship was preserved and some 300 years later, scientists worked together to pull it above water and preserve it. It's amazing that something so old is still in such great condition!
In front of the smaller detailed model they made.
I definitely recommend visiting the Vasa Museum if you go to Stockholm!!