When Australian explorers first flew small planes over the Highlands in 1933, they were astonished. They had thought it was empty jungle. Instead, they saw whole valleys full of neat gardens, villages and tens of thousands of people. The Highlanders were just as astonished to see a plane - many had never met anyone from outside their mountain valley.
The Highlands are cool, misty and very green. The land sits between 1,500 and 2,800 metres above the sea - about the height of the highest mountains in the United Kingdom. Mornings start with fog rolling between the peaks. By midday the sun breaks through and the gardens glow bright green.
Highland families have farmed the same kinds of food for thousands of years: sweet potato (the most important crop, called 'kaukau'), taro, bananas, sugarcane and greens. Many gardens are dug into the steep slopes in long, careful rows so the rain does not wash the soil away.
Today, towns like Mount Hagen and Goroka sit high in the Highlands. They have busy markets, schools and football fields. Children walk to school past coffee plants and gardens of kaukau. Almost every family still keeps a small garden, even in town.