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Photo: Dan Troyka, CC BY 2.0 via Wikimedia Commons
Designed in 1909 by Colonel George Washington Goethals, who went on to design the Panama Canal, this structure is great fun to check out even though it's no longer operating: you can walk along the precipitous edges of the lock and still imagine how freight vessels were conveyed from Bayou Plaquemine to the Mississippi River.
Plaquemine Lock State Historic Site, located in Plaquemine, Louisiana, commemorates an early example of hydraulic engineering design and the historic significance of Bayou Plaquemine, an important navigable waterway that was once a distributary of the Mississippi River. Bayou Plaquemine promoted settlement beginning in the 18th century and helped the area economically by providing an access route between southwestern Louisiana and the Mississippi via the Atchafalaya Basin.
© OpenStreetMap contributors
Built by slaves for John Randolph, this 1850s antebellum estate is reputed to be the South's largest and looks like it could be the White House. It functions as a hotel and restaurant but is also available for tours.