A golden cross sits on top of Germany's highest mountain, the Zugspitze, located in the Ammergauer Alps. This part of the Alps, and the mountain itself, are a big draw for visitors eager to ski, hike, climb or just cruise to the top in a cable car to have some food or a beer. But the mountains are feeling the impact of a warming world — at an alarming rate.

It's September and unusually warm. So warm that some people wear shorts and T-shirts as they stop off to eat and explore the glacier plateau before heading for the summit. Thirty years ago, it would have been much colder here. Since 1985, there's been a warming of around 1 degree Celsius (1.8 Fahrenheit). In the Alps, temperatures are rising twice as fast as the global average.

Increased temperatures mean receding glaciers. Michael Krautblatter, pictured at the Schneefernerhaus environmental research station with the remnants of one of the Zugspitze's glaciers behind him, says "it's just a matter of time before they disappear." The professor of landslide research at Munich's Technical University (TUM) has been studying the mountain's ice for 10 years.

Krautblatter and his team use specialized equipment to measure the Zugspitze's ice and permafrost — a layer of permanently frozen sediment, rock or soil. They place electrodes inside the rocks to measure electrical conductivity. If it's no longer frozen, conductivity is good. The work sometimes involves the researchers scaling the mountain face. The permafrost is disappearing too, they say.

That's bad news, largely because permafrost helps to stabilize the mountain rock. Over the past year, around a thousand rockfalls have been reported, says Krautblatter. Some popular hiking routes have already been closed and a dozen or so Alpine huts are subsiding. It could also be a problem for cable cars, because they are anchored in the rocks on the mountainside.

Scientists aren't the only ones who've witnessed the changes. Toni Zwinger is 33 years old and works at the inn run by his family near the summit. He grew up on the mountain and as a child the glaciers were his playground. He says the glacier is much smaller, the winters are warmer and he hears the rocks shifting outside in the evening when the tourists have gone and the mountain is quiet.

The Münchner Haus opened in 1897 and the Zwinger family has been running it since 1925 — back when it could only be reached by climbers. It's a traditional Alpine hut in which people can stay overnight. Those people can now easily ascend the mountain by train and cable car. That's increased the number of visitors to the peak exponentially.

Even if, as set out in the Paris Agreement, the world manages to limit global warming to 2 degrees Celsius above pre-industrial levels, that would represent warming of around 4 degrees in the Alps. That means less snow, more rain, changing vegetation and no glaciers. It could also mean that visitors will no longer be able to enjoy a beer or hot chocolate at the century-old Münchner Haus.

From August 2018 a new cable car will take visitors up the 1,800 meter high Jenner mountain. A short walk up to the summit is rewarded with a breathtaking view of the Berchtesgaden National Park - which was founded in 1978 to ensure that nature would be able to develop unimpeded. From the Jenner summit you can see the National Park's landmark Watzmann mountain and at its foot the Königsee lake.

The history of Berchtesgaden dates back to the founding of an Augustine abbey, probably in the year 1102. The settlement grew because of the flourishing trade from the local salt and metal mines. In 1810 the abbey came under Bavarian rule and to this day it still serves as a residence for the descendants of the Bavarian royal family. Part of the abbey building is also open to the public.

In the National Park Center "Haus der Berge" you can experience the park with all senses. Forest noises are simulated, natural phenomena explained, and stuffed animals can be touched and patted. A path leads up from the Königsee lake to the summit of the Watzmann mountain. The message of the exhibition clearly states: see nature's beauty - now protect and preserve it!

Majestically it towers over the Berchtesgaden area - the Watzmann mountain is the landmark for this region. The 2,700 meter (8,858 ft) mountain is known for its unusual shape. According to legend evil king Watze once terrorized this region. To punish him god turned him to stone (peak on the right) along with his wife (peak on the left) and his children (the small peaks in the middle).

The lake is located between impressive mountain walls in the Berchtesgaden National Park. The fjord-like lake is eight kilometers long and nearly 200 meters deep - which makes it very cold, even in the summer. Every few minutes environmentally friendly electronically powered boats ferry visitors across the lake.

About half way across the lake the captain stops the boat, pulls out a flugelhorn and plays a melody. Visitors can clearly hear the echo, created by the sound bouncing off the mountain cliffs. In the past small canon were fired - the sound of which would reverberate as many as seven times. But due to the fire hazard these posed on the boats, the preferred choice today is a trombone or flugelhorn.

After about half an hour the electronically powered boats reach the Hirschau peninsula, below the east wall of the Watzmann mountain. It is known for the 17th century baroque pilgrimage church of St. Bartholomew with its red roof and onion domes. Near the chapel lies the old royal hunting lodge of the same name, which today serves as a restaurant and beer garden.

Water loudly cascades through the Wimbach Gorge near the village of Ramsau. Leading through the ravine there are bridges and walkways taking you past 200 meters of steep cliffs. Particularly beautiful is the deep blue color of the Wildbach, brought about by sunlight being broken by the calcium particles in the water. An hour's hike into the mountains from here leads to the Wimbach Castle.

The 51 meter suspension bridge crosses the Klausbach River and valley. This popular hiking destination in the Berchtesgaden National Park is also known as the valley of eagles - with a bit of luck visitors might be able to watch golden eagles soar.

There are numerous mountain pastures in the Klausbachtal valley, like the Bindalm. It is easy to reach by foot or with the pasture adventure bus. Cars are banned from the protected area. The pastures are used traditionally. Cattle can only be found grazing on the mountain pastures during the summer. In the autumn farmers drive them back down into the valley.

On the Bindalm you find Pinzgauer cattle, a bovine breed that is so rare that it is on the Red List of endangered species. At night they are allowed out onto the expansive mountain pastures, and the days are spent in the stables. Mountain farmers use their milk to make cheese which they sell, along with a glass of milk and a slice of bread, to mountain hikers.