This is a 'baby hatch' where abandoned babies can be left by their mothers.
Newborns can be placed in the heated box, lined with a pillow and blankets, so that nurses can retrieve them and take care of them before they are put up for adoption – if their mothers don't return to re-claim them.
The 'Babyklappe' is used at Berlin's St Joseph hospital.
It takes about two or three minutes for staff to get to the hatch so the parent has enough time to slip away unseen.
Inside the box is a letter which tells the mother German authorities will look after the baby for eight weeks.
The system can be like a 'revolving door' as mums that change their mind can come back to reclaim their babies within two months.
However, if the parent does not come back to be reunited with their child after the two months it will be put up for adoption.
The practice was common in medieval times but according to the BBC has been criticised by the UN Committee on the Rights of the Child recently, which believes children have a right to know who their parents are and that right is denied to children left in the baby hatch.
There are baby boxes across Europe but Germany has the most with 99 across the country. Poland has 45, Czech Republic 44, Hungary 26, Slovakia 16, Lithuania eight, Italy eight and Belgium, the Netherlands, Switzerland, Vatican, Canada and Malaysia all have one as of last year.