The term 'PEAK IN HEIDI' is a crossword solution which consists of three letters, ALP. This is an abbreviation for the German word 'Alpen', which translates to 'ALPS' in English. The ALPS are a mountain range located in Central Europe, and the highest peak in the ALPS is Mont Blanc, located in France and Italy. Therefore, the crossword solution 'PEAK IN HEIDI' can be interpreted as referring to the highest peak in the ALPS, Mont Blanc.