Danvers State Hospital was absolutely spectacular; I was fascinated with this place for quite some time and finally seeing it in person was a great experience. Inside the building was pitch black, but there were intervals where boards were off and sunlight allowed in. Some rooms were completely collapsed in, and in the complete darkness it was easy to not notice the missing floor when stepping through a narrow doorway. Most of the hallways were in good condition, but there were a few trouble spots... the ward rooms had definitely been less reliable.
There is a tower in the center front of administration, with four balconies (one for each direction) which gives one a spectacular view from Hawthorne Hill.
The basement was extensive, and there were connecting steam tunnels to the Bonner medical building, but had been sealed by the pouring of concrete down the manholes from above.