Neighbours in the woman's building in central Berlin called the emergency services on Sunday evening, saying that they had noticed her letterbox was full and were concerned.
After knocking and ringing on the door for some time, firefighters forced their way in.
They looked around the flat, finding the woman's corpse in the bathroom in a state of decay so advanced she was unrecognizable, police spokesman Thilo Falk told The Local.
The 52-year-old had lived in the Heinrich-Heine Strasse building for ten years, the BZ newspaper said.
It took several months until one of her many neighbours realized she had not been seen in a while. Police said they were unable to say exactly how long ago she had died.
“She had been there for a considerable length of time,” said Falk.
The BZ reported that investigators believe the woman could have died between the end of August and beginning of September 2013. The paper also said that there was medication found in the flat, suggesting she had been unwell.
“There will be an autopsy and an investigation is underway,” Falk said. At this point officers do not believe there was anything suspicious surrounding her death.
SEE ALSO: Police find corpse watching TV