Final preparations for special Mass with Pope Francis at the Basilica

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Pope Francis will celebrate Mass at the Basilica of the National Shrine of the Immaculate Conception on Wednesday. Final preparations are being wrapped up as crews are making sure no detail is overlooked as they get ready to welcome 25,000 worshippers along with hundreds of members of the media.

About 15,000 chairs, 3.2 miles of cable and 100 moving lights are just part of what is involved in the production at the Basilica.

As musicians rehearse for Wednesday’s papal celebration and Mass, the flowers are planted and the protective wrapping is peeled off the cross.

This is a production that has been in the planning stages for five months and it is almost showtime.

Even Archbishop of Washington Cardinal Donald Wuerl made a surprise appearance to see the final preparations.

Blayne Candy, co-founder of Showcall Inc., the company in charge of setting the stage for Pope Francis, said set up started a little more than a week ago.

His company produced the last papal visit at Nationals Park. He said the stadium's fixed seats made things a little easier. However, there are a few more challenges here at the Basilica.

“We have trees, we have buildings and everything to contend for, and the objective was to try to make this as large as possible within the confines of the campus and the Basilica space,” he said.

A lot has gone into making this event "pope perfect.” They used sophisticated 3D programs to make sure the acoustics and visibility from the seats are just right.

“To account for the slope in the ground, the elevation changes, and what it did is it gave us the capability to really put ourselves in any seat in the house,” said Candy.

In addition to the 25,000 people attending Mass here, there will be 2,500 ordained priests inside the Basilica.

“There's probably going to be another 100,000 down on the [National] Mall that will be watching on a large LED wall,” Candy said.

The United States Conference of Catholic Bishops, the Archdiocese of Washington, the Basilica and Catholic University are footing the bill for this event.

This is being designated as a national special security event, so the Secret Service is overseeing security.