"Helmut Kohl is why we have all this," says Sigmund as he repairs his boat engine on the River Spree. He gestures at the tourist barges, the offices, the construction sites along the river bank. "He brought East and West Germany together."
As the so-called "father of reunification", not to mention the man who took Germany into the euro, Helmut Kohl is still a powerful name here.
Now a new book, Legacy: the Kohl Protocols, based on old interviews offers a tantalising, and not entirely flattering, glimpse of what he really thought about his political peers.
The man himself is a frail 84-year-old. Barely able to speak after a stroke several years ago, he is reported to be completely reliant on his second wife, Maike, who restricts access to the former chancellor.
But his words have still found a way into the public domain.
Angela Merkel, once his protegee, "couldn't eat properly with a knife and fork", we are told.
The Kohls tried desperately to prevent publication.
The book's author - a journalist called Heribert Schwan - recorded 630 hours of interviews with him in 2001.
Schwan was supposed to to write Kohl's memoirs but after the first three volumes the men fell out before the fourth and final book was published.
A court forced the writer to return the tapes, but he made transcripts of them first.
The story they contain is likened to a thriller by the popular tabloid newspaper Bild.
After all, Helmut Kohl. as Germany's longest serving chancellor. was in power during the fall of communism.
Contrary to his public attitude at the time, this historic period had, he believed, nothing to do with people power.
"Gorbachev looked over the books and realised that all was lost and that the regime could not survive," he tells Schwan.
But there's one secret the interviews do not give up.
Mr Kohl fell from grace during a party funding scandal in the 1990s. Under his leadership the Christian Democrats received illegal donations using secret bank accounts.
To this day he's refused to name the donors.
Most engagingly the book reveals a man of contrast.
Here we see a confident leader adept at eliciting cash for his party.
When the car manufacturer Daimler Benz, for example, sent a cheque for 50,000 marks he returned it, replying that the company was clearly in financial trouble. They sent back double the amount.
But there is also the man dubbed "Die Birne" (the pear) in the German press on account of his body shape.
He wanted to be seen as an international statesman but feared he was perceived as a provincial philistine.
Although the book's been published against his wishes, Helmut Kohl is once again at the centre of German gossip.
Will Sigmund read the book? "Of course. Once the boat engine is repaired."