"Usually you can walk in there, obviously we can't walk in there right now," said Soraya Sheffield from Orlando.
Security measures are heightened around the National Constitution Center ahead of the must-watch event scheduled for Tuesday night.
"I've seen it. It's a noticeable presence, you can actually feel it around. I'm surprised they're letting people walk as close as they are, but I definitely see the barricades. It's been quite the experience," said Dwayne Monize from Toronto, Canada.
Over the last several days, barricades were put in place surrounding Independence Mall in preparation for multiple road closures.
Street closures, other changes in Philadelphia you need to know about for the presidential debate
Flight restrictions were also put in place, and there is a notable presence of law enforcement in the area.
"There's plenty of work you don't see behind the scenes," noted security expert Jack Tamarchio.
Tamarchio used to work with Homeland Security. He told Action News that the National Constitution Center is a place that security officials are already familiar with thanks to a number of past high-profile events.
"They understand this place, they have it mapped out. They know where the ventilation systems are. They know where underground piping tunnels are. So those are places they are comfortable with," he explained.
Philadelphia leaders have worked with state and federal partners to secure the debate venue and its surrounding area.
Most roads around Independence Mall are closed as of Tuesday morning, limiting access to the area.
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Action News spoke with Philadelphia Police Commissioner Kevin Bethel, who talked about this monumental task.
"We will have our Office of Emergency Management up and activated tomorrow, and work in collaboration across the entire city government with local state and other partners to ensure we have a safe event," Bethel said.
Another issue authorities are concerned with when it comes to security is whether protests will break out before, during, or after the debate.
Action News spoke with a lifelong Democrat who flew all the way from Florida to protest issues relating to the Israeli-Palestinian conflict.
"This is a major international event. I've already done media with Mexico and Russia, all kinds of people. There are all kinds of neat people I am relating to," said Bob Kunst from Miami Beach.
The Philly Palestinian Coalition is also expected to gather at City Hall on Tuesday night and march down to the National Constitution Center.
Police said they're working with the group to create an atmosphere of expression while also keeping safety in mind.
From barricades to restrictions, security tightens in Philadelphia before presidential debate
On top of that, Trump supporters gathered outside a Center City hotel where the vice president was staying Monday night.
And in Brewerytown, groups gathered outside of a Harris campaign office to protest issues surrounding deportation.
"It's a good day because the vice president is here and we're trying to make our voice heard," said protester Tia Chao.
As the debate draws closer, security will tighten even further, with more road closures throughout the day.
Some tourists said they went to the National Constitution Center on Monday while they still could.
"I was trying to come over here, see what's happening, and maybe do a big watch party from my hotel," said Sarah Kalika from San Francisco, California.
'The ABC News Presidential Debate | Race for the White House' will air September 10 at 9 p.m. It will air on ABC and stream on 24/7 streaming network ABC News Live, Disney+, and Hulu.