With thousands of protesters planning to descend on Philadelphia next month during the Democratic National Convention, the city is readying itself for the possibility of prisoner overflow.

The city's now-defunct Holmesburg Prison will be reopening during the DNC, July 25-28, to hold arrested protesters if necessary, the Inquirer reported.

"If we had to activate Holmesburg, that would be out of necessity for a mass-arrest kind of processing situation," said Shawn Hawes, a spokeswoman for the Department of Prisons."We're always ready to open whenever necessary, so, like the city, we're hoping for the best, preparing just in case."

Hawes added that, if Holmesburg was reactivated, arrested protesters would be held in the prison's recently renovated gymnasium, not the cell blocks. Processing a person typically takes from 8 to 24 hours before they can post bail or are transferred to another facility.

The gym has 100 beds, showers and air-conditioning, Hawes said. 

Philly has issued 13 demonstration permits so far, and the city expects more than 50,000 people to attend protests alone, but the city said it doesn't plan to crack down on protesters demonstrating without permits, PhillyVoice reported.

Still, Bernie Sanders supporters practiced getting arrested last weekend ahead of convention concerns.

Built in 1895, Holmsburg is notorious for a violent past that has included shootings, stabbings, beatings, rapes, riots and decades of human experimentation.

Renowned dermatologist Albert Kligman's experiments on inmates eventually became a catalyst for federal restrictions on human testing, the New York Times reported at Kligman's death in 2010. 

For nearly two decades, Kligman conducted research on behalf of pharmaceutical companies and government agencies to test household products, like deodorants and shampoos, and toxic, hallucinogenic and radioactive materials.

Prisoners were deliberately and directly exposed to pathogens like the herpes virus and the athlete's foot fungus.

When it closed in 1995, the city transitioned to the nearby Curran-Fromhold Correctional Facility.