Max Key has posted a photo of himself at the Jewish Memorial in Berlin, to mark the end of the European leg of his world trip.
John Key's son has finished four months of travelling around Europe and has now started a three-month stint of travel around Australia and Asia.
Max Key said on Instagram he spent three days in Berlin to learn about his Jewish heritage.
His paternal grandmother, Ruth Key, was an Austrian-Jewish refugee and his father has spoken proudly of the family's Jewish roots.