Cut out the flesh of the melon with a ball cutter. Wash the apple, cut it in half, remove the seeds and cut it into slices. Peel banana and cut into slices. Mix the fruit and divide half of it into 4 dessert glasses.
Add 1 scoop each of strawberry and vanilla ice cream. Spread the rest of the fruit, muesli and maple syrup over it. Decorate the sundae with lemon balm and serve immediately.