There is a secret Buddhist temple in Gonzales, LA (although I've never found it) as well as an Eastern tea garden and pagoda at Houma's House.
I don't think it's really a secret to people who live there, but The Fly is a park on the river side of the levee in New Orleans behind the Audubon Zoo.
Holly Beach in Cameron Parish is actually a real beach with legit sand and everything! There's no buildings save mobile homes sense Rita annihilated Cameron back in 2005, but it's basically the only real beach in Louisiana.
The Plantation where they filmed the horror movie "The Skeleton Key" is a private residence just down the road from Oak Alley Plantation.
Port Hudson north of Baton Rouge has a Civil War battlefield and puts on an annual reenactment in the spring.
NOLA Brewery offers tours and frequently holds parties with live bands and lots and lots of free beer on tap.
This post was edited on 9/18 at 4:05 pm