"Hidden beneath our cities, unnoticed on high mountainsides.
The more exploring you do, the more abandoned places that you find."
In 2015, Happer published a book, "Abandoned Places: 60 Stories of Places Where Time Stopped," that celebrates the eerie sites around the globe devoid of human residents.
"Abandoned Places" explores deserted sites on Antarctica, islands in the middle of the Pacific, and even a Six Flags in New Orleans.
A nuclear power plant explosion at Chernobyl in 1986 coated this northern Ukraine city in radioactive material.
Pennsylvania's Eastern State Penitentiary, opened in 1829, introduced a new prison model by isolating inmates and subjecting them to labor.