Nada Prlja's black stone wall, called the "Peace Wall", is 12 metres (yards) long and 5 metres high and bisects Berlin's central Friedrichstrasse, just south of Checkpoint Charlie, a famous former Cold War border post and today a major tourist attraction.

"The new wall underlines the gap between the upper Friedrichstrasse - characterized by fancy shops and expensive flats - and the poor southern part of the road which heads to the multi-ethnic Kreuzberg district," said Denhardt von Harling, spokesman for Berlin's Art Biennale show.

The Peace Wall, is part of the Biennale, which this year focuses on political art, and will stand for two months.

The art installation is intended to challenge the gentrification underway in the area over the last few years and highlight the huge wealth gap.

The 3.3 km Friedrichstrasse passes through the heart of Berlin's rebuilt city centre. Just beyond the site of the former wall glittering glass office blocks begin to give way to 1970s social housing, luxury boutiques are replaced by charity shops and the crowds of tourists and office workers disappear.

The sudden change is uncanny.

"A wall is a symbol of division, and is in itself capable of highlighting invisible gaps," said Prlja.

"'What are the major causes of gaps in our society?' I asked myself," the artist said, adding she identified social segregation, poverty and origins.

Prlja's wall has brought mixed reactions.

"I really do not like it" says Younes Alkhatib, a barber on the "poor side" of Friedrichstrasse.

"I come from Palestine and this wall reminds me of what happened in Israel. Divisions always spread a negative message...Pointing out divisions does not help to solve them."

Hawach Amim, another Palestinian who works on the "poor side" said: "That black wall makes me think of a funeral."

"When I look at it I think of the previous Berlin Wall. Raising walls makes people enemies".

Prlja concedes her installation may stir fears by making people face reality, but she said she wants them to look at the "Peace Wall" and fight for their rights.

There is also praise for her work.

"The wall is really a good idea", says Frank Wille, store manager in a charity shop. "It really addresses the problem we have been experiencing in the Friedrichstrasse for years. The street is visibly divided. This time art has fulfilled its task of being bold, provocative and socially engaged."

(Reporting By Elisa Oddone; Editing by Alexandra Hudson and Paul Casciato)

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