(noun)
a facility where people are offered long-term care and/or treatment in the form of therapeutic regimens of diet, exercise, and fresh air while they are recovering from an illness;
e.g. He went to a sanatorium so that he could regain his health faster.
(noun)
an establishment that provides long-term care to people suffering from chronic illnesses or people broadly seeking recovery or healing;
e.g. They went to a sanatorium to heal from the trauma they had suffered.