Beth Sholom Synagogue in Elkins Park, Pennsylvania, began with a letter. And that letter contained a very bold, and very specific, proposition.

In it, Rabbi Mortimer J. Cohen outlined his vision for a synagogue that was simple and modern in design. It could hold 1,200 to 1,500 people, and would cost $500,000. This synagogue would have no windows, but it would have a roof with glass and a rotunda in order to let in light. Walls would be acoustically treated. There would be classrooms and meeting rooms and storage rooms, and it would all be air-conditioned. He included sketches of his vision.

Twelve days later, Rabbi Cohen received his response: “Dear Rabbi Cohen, I would like to talk with you concerning your project.” It was signed Frank Lloyd Wright.

Yes, Rabbi Cohen explained to the master architect himself how to design the synagogue. But Wright embraced the vision—it was similar to a cathedral he had designed in the 1920s, which was never built. And this exchange of letters marked the beginning of a six-year collaboration between the rabbi of a Conservative Jewish congregation, founded in Philadelphia in 1918, and one of America’s most prominent architects.

“And it truly was a collaboration,” says Helene Mansheim, the visitor center and retail manager at Beth Sholom Synagogue. She notes that when Wright sent the first set of plans for the synagogue in 1954, he gave Rabbi Cohen co-designer status.

While Rabbi Cohen laid out his vision for the synagogue, Wright approached it with a clear intent: He wanted congregants to walk in and feel “as if they were resting in the very hands of God.”

The seats are arranged in a horseshoe formation on a gentle slope, in such a way that no matter where you’re seated, you can see others around you.

“You’re not in a space where all you see are the backs of heads and profiles,” Mansheim says. “You see people. And that’s very different.”

Then there’s the natural lighting, which filters in from the pyramidal glass tower. “If you’re in there on a bright, sunny day, and a cloud goes overhead, the whole room darkens,” Mansheim says. “You can see shadows sometimes when a bird flies close enough. If you’re there at sunset, the room turns gold. And when the sky is blue, you see blue. It’s amazing.”

The synagogue was dedicated on September 20, 1959, five months after Wright’s death. It was the only synagogue he ever designed.

It continues to look much the same as it did on the day of its dedication, although there was a major recent effort to make the building more accessible. Architects with John Milner Architects added an elevator to make all levels accessible, upgraded existing restrooms to ADA standards, and widened sidewalks, among other key upgrades. For these modifications, the synagogue received a 2016 Grand Jury Award from the Preservation Alliance for Greater Philadelphia.

Regular maintenance and upkeep have kept the synagogue in excellent condition, even as it sees a huge amount of foot traffic throughout the years, both from congregants and visitors who come for a tour.

“We’ve always had people knocking on our doors with cameras,” Mansheim says. “That’s always been the case.”

But it wasn’t until 2009—two years after Beth Sholom Synagogue was listed on the National Register of Historic Places—that a formal tour and visitor center was established. In that time, people from all over the United States and 68 countries have passed through its doors.

Visitors can take a guided tour, watch a 20-minute documentary film about the synagogue (narrated by Leonard Nimoy), and study the exhibits in the visitor center, which explore topics including the synagogue’s construction, its architectural features, and the experiences of multiple generations of Beth Sholom Congregation members.