By John McDevitt

PHILADELPHIA (CBS) — Eastern State Penitentiary national historic site is getting ready to hold its biggest fundraiser of the year.

“Terror Behind the Walls” is in its 27th year. It’s six haunted houses in one. New this year is “Blood yard.”

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“Deep with in the ruins of the prison compound you discover a camp of a gruesome colony,” said creative director Amy Halloman.

A path marked in bones leads you deeper and deeper into the layer of the butcher, the warriors and the ancient emperoress, and beware you could be ambushed by the creatures at any time like the unexpecting media gathered near the podium for the announcement.

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To our delight we were spared and they just went away.

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“Terror Behind the Walls” opens Friday and runs on selected days through November 11. More at