Near the center of Newtown, Connecticut, there is an old colonial-style campus that could be mistaken for a typical New England college or boarding school. Town residents walk their dogs next to colonnaded red brick buildings and jog through the hundreds of acres of surrounding forest and pastures.

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But buried beneath the grounds there is a system of deep tunnels, leading not to lecture halls or the student union, but to confinement rooms, psychosurgery laboratories, operating rooms, and even a morgue.

For most of the 20th century, the tunnels were used to shuttle psychiatric patients between their treatments, in what grew to be Fairfield State Hospital, also known as Fairfield Hills, one of the largest psychiatric institutions in New England.

The state-run hospital treated patients from the early 1930s until it was shut down in 1995. Over the decades, the facility expanded from 500 beds in the early years, to over four thousand at its peak. And although it was built as a way of easing the overcrowding of two other Connecticut facilities, the ratio of the medical staff to patient was always a challenge, averaging 200 to one for doctors, and 80 to one for nurses.

Since the last residents were moved to other facilities in 1995, the campus has sat mostly vacant, its buildings slowly crumbling and tunnels sealed off. Its fate rests in the hands of the town of Newtown, which acquired the entire parcel from the state in 2004, and there have been various redevelopment plans that have come in fits and starts. Today there are a few buildings in use, and several trails and park areas are open to the public.