Neuberlin is the Nazi capital of the planet Himmel. The city was built at the former planetary capital of the System Lord Nirrti and her minions after Nazi colonists crashed there. In the following 60 years they have remade the city in their image using the Wagnerian visions of Albert Speer. Himmel's Stargate is placed in an underground concrete bunker outside Neuberlin.
The city is built on a large hill overlooking a forest in all directions. A wall surrounds the city but this area was quickly extended by the thousands of colonists who needed living space. The huge structures Nirrti had built are now used as administrative buildings and places for members of the Governing Council. Shiny white marble mined from the nearby mountains has replaced the grayish stone favored by the System Lords. Large pillars flank the main building, while the Eagles and statues of fallen heroes dominate the city boulevard. The centerpiece is a huge sculpture celebrating the glory of the Aryan people, a man and a woman standing together and reaches up to the sky.
Life in Neuberlin is a strange combination of modern lifestyle and siege mentality. A governing council of Führers represent the various branches of the Nazi Party, armed forces and specialty groups like the SA. Colonial citizens are expected to engage in the "higher cause" and obey the Council decrees as they would the Führer himself. Himmelite slaves do most of the heavy lifting, leaving the colonists free to join the army or exercise more esoteric interests. Crime is virtually nonexistent beyond shoplifting, since most colonists have a strong work ethic. Several factories are on the outskirts of the city near a river where industrial waste is dumped. They use the vast majority of settlers (along with a fair sampling of Himmelite work) and produce everything that can not be grown or otherwise obtained from a natural resource.
This is the colony's main source of war machines and weapons. Himmelite is a never-ending threat and each colonist know what would happen if they ever got the upper hand. Himmelite slaves are relegated to labor camps and the like away from the colonists. The Nazi consider them little more than pack animals, and while they take steps to keep them alive and healthy they have no real rights over the colonist regime. The camps are kept under constant guard as well as factories, mines and other fields that depend on slaves to work. But the Himmelite have a plan. In recent years they have purposefully allowed some of their number to be caught and to participate in the workforce. These spies learn as much as they can before trying to flee to his tribe to relate what they have found. Eventually they hope to discover some key to defeat their enemies forever. If they ever get any kind of advantage the Himmelite would not hesitate to wipe out the Nazis to a man. The colonist army is well equipped, with their armor extended with reverse engineered human weapons and other technology captured from Goa'uld. They also have a couple of tanks and fighter craft on par with the modern U.S. military and their weapons are superior to that of the SGC in many ways.
The Himmelite numbers and knowledge of the terrain has proved an apt match for them. Without more resources the colonists have not developed enough weapons to crush their enemies once and for all. Some research facilities are also located within the city, working to understand and adapt Goa'uld technology. The stargate is a topic of little interest, the colonists thinking it's a one-way channel that naturally leads only back to Earth. In their joy to unlock an address, the Nazis never determined that the return address can be different. In the beginning, they made numerous attempts to contact their country, all of which ended in failure (it had been sealed up by Rommel and eventually captured by the Americans).
With no way back home, the colonists more or less left the gate to gather dust while many hope that one day their cousins on Earth will return through the wormhole to deliver news about the inevitable Nazi triumph and perhaps reinforcements to help them complete their conquest of Himmelite. (RPG: "First Steps: The Stargate Unexplored Worlds Roleplaying Sourcebook")
The RPG states that Paul Langford is German and brought the Stargate to Germany after it was discovered. Hitler saw the gate as an occult treasure and organized an attempt to unlock its power. They managed to activate it and traveled to Himmel to colonized it. Langford saw what it did and thought they were all crazy. He defected to America and convinced them to capture the gate, which they did. However, later in the series, and in "Stargate: Continuum", this is retconned, stating that the gate was brought to America in 1939 before the Nazis could their hands on it.