However the walkers, joggers and cyclists weren't alone. They were joined by officers from the Philadelphia Police Special Victims Unit and by Police Explorer cadets - all offering a serious warning and a reminder.
The Fairmount Park rapist, who first struck ten years ago this week, remains at large.
"He's still out there. He's still unidentified and still on the loose. We're trying to raise more awareness, generate more tips and bring this to a good conclusion," said Lt. Anthony McFadden.
The same suspect is believed responsible for the July 2003 rape and murder of medical student Rebecca Park near the Chamounix stable, and an October 2003 attempted rape by the Falls Bridge.
DNA also matched that suspect to an August 2007 rape in Pennypack Park.
Police are looking for tips and also reminding people to remain alert while enjoying Fairmount Park.
Mary Ann Wilmarth, who's visiting from Massachusetts, said she appreciated the heads-up.
"I thought it was a good thing to have that awareness. Coming down from Boston, there has been a lot going on the past week, so we are all very aware of what's going on. I thought that was great," said Wilmarth.
Several young runners say they'll be sure to take precautions.
"I just make sure I'm with a group of people and always looking around to be alert," said Gloryna Reveil.
Some people might think efforts like these might not generate new tips. However police say that's not true and they continue to work this case every day.
Anyone with information can submit a tip by calling 215-686-TIPS (8477), texting a tip to PPDTIP (773847) or through PhillyPolice.com.