A view into a cell in D Block. D Block held the most difficult prisoners. Solitary confinement cells had no light, were colder, and the food was, (for the worst,) just bread and water, with full meals, just twice a week. Showers were once a week for 10 minutes. Exercise was for one hour, once a week. Alcatraz was a maximum security Federal Penitentiary until 1963. Extremely violent offenders, and prisoners who caused trouble in other prisons, were sent to Alcatraz. The island is now under the care of the National Parks Service. The cellblock, and grounds, are a major tourist attraction. California.