The men incarcerated at New-Gate were kept in a pit beneath the ground in an old copper mine. Those who were incarcerated underground in Newgate Prison were subjected to cold, damp, and dark conditions year-round— tuberculosis became a common occurrence, and the prisoners were unsupervised with limited comforts or access to proper medical care. The built-in containment within the mine also included a separate section designated for solitary confinement. Due to its secluded position and the protective features of its two vertical shafts, the Colony of Connecticut opted for the mine as a suitable prison location. The first shaft, measuring 35 feet deep, had a ladder fixed to its wall for access and was further secured with a grate at the entrance. As for the second shaft, which reached a depth of 75 feet, it lacked convenient means of entry, leading the prison overseers to consider additional security measures unnecessary.
See it for yourself virtually: https://www.capturepics.com/3d-model/old-new-gate-prison-copper-mine-the-coppermine/fullscreen/
 The Rise and Fall of Newgate Prison. YouTube. Connecticut Humanities , 2018. https://www.youtube.com/watch?v=ZvRYObAJB78.
 “First New-Gate Prisoner – Today in History: December 22 – Connecticut History: A CThumanities Project.” Connecticut History | a CTHumanities Project – Stories about the people, traditions, innovations, and events that make up Connecticut’s rich history., April 26, 2023. https://connecticuthistory.org/first-new-gate-prisoner-today-in-history-2/.