An artistic project to lay stones marking buildings that were once home to Jews deported by the Nazis has run into problems in Munich, as authorities fear they will be targets for anti-Semitic attacks.
They are small and at first you don't notice them on the ground as you walk past. But look down, and you'll see them. They are brass plaques with the names of the victims of the Holocaust engraved on them.
"Helene Plaut lived here. Born in 1862. Deported in 1942 to Theresienstadt. Murdered in Minsk."
Artist Gunter Demnig has investigated thousands of cases
The stones arts project has been created by a German sculptor, Gunter Demnig.
He first had the idea in the early 1990s when he was unveiling a memorial for the Sinti and Roma victims of the Holocaust.
An elderly woman approached him and insisted that "no Gypsies ever lived here".
Shocked by her denial, he investigated the city's history, finding plenty of evidence that thousands of Gypsies and Jews had lived next door to Germans in the 1930s.
"It is so easy for people to deny something. I wanted to ensure that this would not happen," he says.
His workshop in Cologne is packed with brass plaques, stones and maps of Germany. Each stone is personally crafted by the artist. He calls them "Stolpersteine", or "stumbling-blocks".
"You should stop when you see these stones, look down, bow your head and then look up at the house where the person lived - it's a form of respect," he says.
He walks away to get a glass of water - he is sweating and his voice is breaking.
"It can be a very emotional experience when I go with the families of Holocaust victims to lay the stones in the ground. I read the names out when I see them on the lists I am given - for example, a mother and two children who were deported to Auschwitz."
He stops talking abruptly and I notice that he's crying.
"Sometimes it is all too much," he says.
Mr Deming laid the first stones in Berlin and Cologne four years ago. Now, there are more than 3,600 stones across Germany in 45 cities. Anyone can commission a stone.
It only costs 95 euros (£63). Before a memorial plaque can be ordered, the artist needs records of the victims. He relies on the help of historians, local authority documents and even schoolchildren who conduct their own research.
"Outside this house there are more than 20 stones. This was a Judenhaus," explains Barbara Becker-Jakli from the National Socialist Documentation centre in Cologne, pointing at a modern building.
"Jews were deported from this house and taken to concentration camps. These stones are a personal reminder - it is important that everyone remembers."
While the idea has found resonance in many German cities, in Munich, the authorities have banned the project. Mr Demnig had placed two stones on a pavement in the city before seeking permission.
The plaques were removed by the authorities, and now lie in the city's Jewish cemetery. Opponents of the project say they have based their opposition on the opinion of the Jewish community, whose board had strongly disapproved.
"We have many memorials to the Holocaust here in Munich, so we don't need these stones," says Marian Offman, who is from Munich City Council.
Authorities fear the stones will be targeted like other Jewish sites
"Neo-Nazi skinheads will walk over the plaques and wipe their dirty boots on them. Jewish cemeteries have been desecrated - these stones will also be desecrated."
But for Isaak Behar, whose parents and sisters were killed in the Holocaust, the stones are an important part of remembrance.
"A few years ago, four stones were laid in the ground for my family outside my old home. I have never set foot there since my parents and sisters were taken from the house in 1942. They were then murdered in Riga. These stones are a personal memorial."
Mr Demnig is saddened by Munich's rejection.
"My idea was to bring the names of people who were killed to the houses where they had lived, to the present-day. My stones are individual tributes - they are not large, abstract memorials to the Holocaust.
"The stumbling blocks commemorate all the victims of the Holocaust - including Jews, gays and trade unionists. It is important for people to remember."
He says he is not planning to make a factory at his workshop in Cologne, adding that he has no intention of making six million stumbling-blocks.
"I am an artist," he says. "For me, it is not important how many stones I make. Each plaque is important."