The German Left and Green parties have both criticized plans to set a cross atop the reconstructed Stadtschloss in Berlin, which is to house the Humboldt Forum, a center for art and communication.

The Left's national parliamentary party's spokeswoman for cultural affairs, Sigrid Hupach, told Die Welt newspaper that the proposed cross went against the government's declared intent to erect "a museum of a new kind for the whole world community."

"It is meant to be a public building in which all feel welcome. But how is such an open dialogue of cultures to succeed when a cross on top of the dome already establishes the direction? I think this kind of hierarchization of cultures and religions is absurd," she said.

The leader of the Greens parliamentary party in the state of Berlin, Antje Kapek, said "reducing the Humboldt Forum to one religion" was not in keeping with the basic principles of humanism.

"The new Berlin Stadtschloss is intended to serve the exchange between all cultures," she said, adding that donations made for the building were meant to be used to put up the facades.

The Stadtschloss, seen here around 1900, once dominated the Berlin cityscape

'Need for a secure identity'

The planned cross also has its supporters, however.

"Setting up an open house of the kind that the Humboldt Forum is meant to be is credible only if we are aware of our own roots and show them," said Monika Grütters, the German commissioner of cultural affairs, who belongs to Chancellor Angela Merkel's Christian Democrats.

"Only those who are sure of their own identity can give free scope to others without feeling threatened," she told Welt. "For me, that is what the cross stands for, and that is why I feel it is part of the the palace."

Grütters: "The German open culture has Christian roots"

The Catholic archbishop of Berlin, Heiner Koch, also welcomed the planned cross, saying the symbol was "the sign of the good news of the Christian faith for all people."

However, he called on both sides in the debate to remain calm, saying that "the cross must not become a topic for quarreling over."

"We Christians believe that the cross embodies salvation and hope and life. Fighting and quarreling would take away its meaning," he told the Welt.

The controversy over the cross comes as a heated debate rages in Germany about a so-called "Leitkultur," or "dominant culture," advocated by some conservative politicians as a guideline for the integration of non-German nationals.

Read here about the "Leitkultur" debate

The building was severely damaged in the Second World War

Major landmark

The Stadtschloss, which in the original version had a cross on top of its dome, was once the most dominant building in the historical center of Berlin but was heavily damaged by Allied bombing in World War II. Although the damage could have been repaired, the palace was demolished in 1950 by East German authorities, who eventually built the Palace of the Republic on the site.

That building, which was found to be contaminated with asbestos, was finally demolished in 2009. The reconstruction of the entire exterior of the palace, except for one side, in the original style began in 2013 and is to be concluded in 2019.

The Humboldt Forum that it is to house is named after Wilhelm von Humboldt (1767-1835), a Prussian scholar, author and statesman, and his brother Alexander, a natural scientist.