A German zoo is in line for a $22 million (£16.8 million) windfall after an American couple pledged to give their fortune to "someplace where it would do good".

According to a report in Cologne's Stadt-Anzeiger newspaper, the 93-year-old widow Elizabeth Reichert said she intends to make good on her Jewish husband Arnulf's wish to donate millions to the zoo in his city of birth. 

The couple met in Cologne in 1944, while Arnulf was hiding from the Nazis. They married and left Germany after the end of the Second World War and emigrated to the United States, via Israel. Arnulf began working in a pet food company before establishing a business of his own.

The couple did not have any children and discussed where to bequeath their fortune before Arnulf's death in 1998.

"When you think about leaving money, memories play a major role," Mrs Reichert told the German newspaper, adding that the couple "never forgot Cologne".

Mrs Reichert began sending money to the zoo in monthly installments of €6,000 in 2015, but has now established a foundation for the balance of a reported $22 million. 

The zoo will receive $1 million per year, even after Mrs Reichert's death, and the South American section of the zoo will be named after the late Arnulf Reichert.