...Nothing.

Well, not much.

Fort Gorges, one of Maine's most recognicable landmarks, is an old Civil War-era fort that sits out in the middle of Casco Bay on Hog Island Ledge, about halfway between Portland's Eastern Promenade and Little Diamond Island.

It was built in the 1850s, but it was never used. No troops were ever stationed there, and it wasn't a part of any battles or incidents during the Civil War.

Interestingly, it's similar in size and construction to Fort Sumter in South Carolina, the famous site of the first shots of the Civil War.

The following is from the Wikipedia entry on Fort Gorges:

The Fort's armament consisted of thirty-four 10-inch Rodman guns mounted in the fort's casemates. In 1898, all guns were removed from the fort except a large 300-pounder (10 in (254 mm)) Parrott rifle which was on the top of the fort but not mounted. The 300-pounder Parrott rifle still remains in place and is one of the largest surviving specimens of Civil War vintage artillery. The fort was last used by the Army during World War II, when it was used to store submarine mines.

Today, the fort is a public park, owned by the City of Portland. You can boat out to the island and tour the powder magazines with flashlights. Very cool!