Rabbi Tovia Ben-Chorin, Father Gregor Hohberg and Imam Kadir Sanci hold symbolic bricks in their hands while standing at the construction site of the future "House of One" at Petriplatz in Berlin. (Carsten Koall/Getty Images)

After officials in the German capital offered his parish a prime site to build a new house of worship, the Rev. Gregor Hohberg had a kumbaya moment. Why not transform a city stained by the Nazi era into a place of spiritual healing by building a church, a mosque and a synagogue all under one roof?

During a time of global religious strife, a unifying project involving Christians, Muslims and Jews, the Protestant pastor reasoned, would reverberate beyond Berlin’s borders. They would call it the House of One.

“You can live your faith, but also tear down walls,” said Hohberg, 46, who took inspiration for the idea from the teachings of Martin Luther King Jr.

What once seemed like a pipe dream is now gathering steam. After a sign-off from the city, a design was selected following a major architectural competition. Counting on a newly launched fundraising campaign, organizers hope to break ground within two years. The plan is part of a nascent movement to build innovative religious bridges, including the Tri-Faith Initiative in Omaha that is seeking to put a church and a mosque on the same site as a recently built synagogue.

But even as prospects advance for Berlin’s House of One, the pioneering project has become an example of the still formidable hurdles facing those trying to promote religious unity.

The hands of Rabbi Ben-Chorin, Father Hohberg and Imam Kadir Sanci are see as they hold symbolic bricks in their hands. (Carsten Koall/Getty Images)

Among all faiths, the project has garnered substantial moral support. But it also has its detractors. Some in Berlin’s largely Turkish Muslim population, for instance, have angrily charged the progressive imam now involved in the project with violating the Koran by joining hands with other faiths. Other Muslims in the city, meanwhile, remain skeptical of the Islamic association he belongs to — the Forum for Intercultural Dialogue — because its honorary chairman is Fethullah Gülen, a contentious Turkish religious leader living in the United States.

There are reservations within Berlin’s Christian and resurgent Jewish populations as well, including from some who claim the chosen design makes the structure look too much like a mosque. Yet perhaps the single biggest challenge is overcoming apathy in a highly secular city that has become Europe’s hub of underground youth culture, and where the majority of residents these days have no religion at all.

“I think there is some support for this project, but if you look at the present situation, many people don’t care about religion anymore,” said Manfred Gailus, a professor of modern history at the Technical University of Berlin. “You might get some people who say, ‘Oh yes, it’s a good idea,’ and ‘I sympathize,’ but many others will say, ‘Is it really necessary?’ and ‘How much will it cost?’ ”

That uphill battle has been reflected in efforts to raise the $55 million needed to construct what would be a monolith of blond bricks illumined on the inside by beams of diffused sunlight. Though planners hope to raise the $12.7 million required to start construction within two years, the project organizers have only managed to take in about $102,000 since their drive started in July. At that rate, it would take more than two decades before enough money comes in to lay the first bricks.

But the House of One’s advocates say it is far more notable that the project has managed to come this far at all. It has a secured a historic site and the backing of the city. It has factions on board from all three faiths. And particularly as they begin to cast a wider net for funds — including an effort to tap the wallets of Jewish families whose relatives fled Germany to the United States during Adolf Hitler’s reign of terror — advocates say they have faith that the project will overcome all hurdles, financial and spiritual.

The project is now pivoting around three clerics from each major monotheistic faith: A Christian reverend who lived the repression of East Germany and saw the power of unity after the fall of the Berlin Wall. A young, starry-eyed imam born in Frankfurt and eager to build cultural bridges between Muslims and non-Muslims. And a rabbi of German Jewish stock who fought for Israel in three wars and is now bent on healing old wounds.

“This is the city where the annihilation of the Jews was planned,” said Rabbi Tovia Ben-Chorin, 78, who is spearheading the synagogue portion of the House of One. “But we will now take Berlin from being the city of wounds to being the city of miracles. The city where we begin to change people’s minds.”

Some critics, however, are questioning the decision to build the House of One on a parcel of land at least somewhat linked to Berlin’s Nazi past. They note that Walter Hoff, a Protestant cleric who died in 1977, was pastor of the church that once stood on the site during World War II. Hoff is known to have taken up arms in the Nazi campaigns on the Eastern Front, where he was suspected of taking part in the rounding up of Jews.

Ben-Chorin and others involved in the project insist that the site’s history will not be whitewashed in materials to be displayed inside the House of One. And the high-profile parcel of land, they say, is perfect in other ways.

Sitting in the heart of ancient Berlin, the land has been the site of a series of churches since the 13th century. The wreckage of its last standing church — bombed in World War II — was turned into a parking lot in the 1960s by the former communist masters of East Berlin. So reclaiming the site now in the name of faith, advocates argue, will be highly symbolic.

The House of One is designed so that each faith will worship in separate chambers, although all will enter through a dramatic main hall fitted with a viewing platform boasting dramatic city views. The organization’s bylaws state that no faith can proselytize within its walls, and each must openly welcome all denominations — as well as those with no faith — as observers.

The three clerics — Hohberg, Ben-Chorin and Kadir Sanci, an imam — say that thus far, the strongest skepticism has come from Berlin’s Muslims. The House of One received several rejections before finding an imam willing to participate. And once Sanci was on board, he received a series of negative comments via Twitter and Facebook.

One critic, who went by the name Emel Alperen on Facebook, sent Sanci a quote from the Koran:

“O you who believe! Do not take for guardians and confidants those who were given the Book before you as to make a mockery and sport of your religion.”

Sanci said he did not respond. But in retrospect, he says he would have replied by citing another verse in the Koran: “It may be that God will bring about love and friendship between you and those of them with whom you are in enmity. God is All-Powerful, and God is All-Forgiving, All-Compassionate.”

Stephanie Kirchner contributed to this report.