Thirty-three years ago, David Adelman used his bar mitzvah money to buy a $2,000 stake in Campus Apartments, the student housing business owned by his mother's lifelong friend Alan Horwitz. It paved Adelman's entry into what's now a national network of student apartments that he has come to lead.

Now "Uncle Alan," as he was once affectionately known, has returned the favor 1,000-fold with a $2 million donation to another venture currently helmed by Adelman: the plaza commemorating Holocaust victims that opens Monday on the Benjamin Franklin Parkway in Center City.

In return for that gift, the site will be dubbed the Horwitz-Wasserman Holocaust Plaza in honor of Horwitz and Adelman's grandfather, Sam Wasserman, who died in 1991 at 81.

Wasserman escaped during an uprising at the Sobibor extermination camp in what is now Poland after losing his wife and children there, then raised a second family in the United States, Adelman said. Horwitz, who was young when his own father died, stuck close to Wasserman growing up, which positioned him to become a mentor to Adelman in later years.

"It's like honoring my dad," Horwitz, 74, said of the decision to share the memorial's naming opportunity with Wasserman.

The plaza, which is scheduled to open at a ceremony attended by Mayor Kenney and other elected officials, fills most of the triangular site at Arch Street and the Benjamin Franklin Parkway behind the Monument to Six Million Jewish Martyrs, a bronze sculpture completed in 1964 by Poland-born artist Nathan Rapoport that depicts human bodies engulfed in flames.

By the early 2000s, the Philadelphia Holocaust Remembrance Foundation, which held yearly events at the monument, decided that it deserved a better backdrop than sparsely landscaped patches of grass and cement and began looking for ways to improve the plaza.

Inspired by the story of his grandfather, Adelman joined the foundation and worked on an earlier site proposal entailing an educational center designed by Moshe Safdie, the architect behind Israel's main Holocaust memorial, Yad Vashem.

That plan, which would have cost as much as $50 million to complete, was derailed by the last decade's recession, said Adelman, who by then had become Campus Apartment's chief executive, leading the expansion of Horwitz's West Philadelphia-centered rental business into a national developer of big student housing complexes.

The memorial plaza plan lay dormant until 2015, when the cause was adopted by the Jewish Federation of Greater Philadelphia, led by members of its active real estate industry subgroup, including Matthew Pestronk, president of developer Post Bros., and Jacob Reiter, an executive at Verde Capital Corp.

The backers pushed for a scaled-back approach that resulted in what's to be unveiled Monday on the city-owned property.  The Holocaust Remembrance Foundation, which Adelman now chairs, is paying a nominal rent to lease from the city for 80 years.

Arranged around the new stone-paved plaza are rail tracks from outside the Treblinka death camp in Poland, a grove of trees to represent the woods where partisan freedom fighters hid as they battled the Nazis and their allies, a digital eternal flame, and other symbolic features to inspire reflection on the early 20th-century genocide.

The foundation is collaborating with the Steven Spielberg-founded USC Shoah Foundation at the University of Southern California and the Anti-Defamation League on a rotating series of smart-phone-based guides to the memorial that explore the Holocaust and other instances of genocide and racial hatred.

"We go light on the structure and heavy on the technology," Adelman said. "We're trying to create a place of contemplation and a place of education."

To sustain that vision, the foundation calculated that it would need an endowment of several million dollars, beyond the $7 million it cost to build the memorial itself, to sponsor programming and maintain the site.

With the completion date approaching and the naming opportunity on the table, Horwitz said he was happy to help his acolyte see the plan through, as he had done in the past for Adelman's ventures within their company.

"Any time David needed whatever he needed, I was always there to take care of it," Horwitz said. "It's just the other things have been business. … This happens to be the Holocaust."