In Victorian England, a growing population and a lack of medical understanding resulted in a proliferation of so-called insane asylums that were soon present in nearly every county in the country. The institutions existed to treat "pauper lunatics" -- anyone from the chronically afflicted to people with drug addiction, learning disabilities, and even "pregnant single women who had been cast out by their relatives," according to the British Journal of Psychiatry.
From 2005 to 2010, photographer Daniel Regan explored these derelict structures full of dusty sunlight, old beds, personal artifacts, medical equipment and file cabinets, producing a photo series called "Abandoned."
He said these buildings were essentially walled cities that housed thousands, some of the complexes including cinemas, theaters, hair dressers and dentists. And today, many of them are empty.