expression, ichidan verb
visit someone in hospital
Used when going to a hospital to see a patient, not for one's own medical appointment.
友達が入院したので、病院を訪れた。
My friend was hospitalized, so I visited them in the hospital.
見舞う is a more common and direct verb for visiting someone in hospital or checking on someone's condition. 病院を訪れる is a slightly more formal or literary expression.
Phrase composed of 病院 (hospital) + を (object marker) + 訪れる (to visit).