Port Luna is the second-largest city on Luna, located in the southwest corner of Mare Tranquilitatis and surrounding Tranquility Base National Park. The city has a population of 35,000 and is the largest single 'Danelaw enclave off-Earth.
Port Luna began life as an outpost of the United States Coast Guard and the US Parks Service dedicated to maintaining the area around Tranquility Base, keeping it free from vandalism. As tourist traffic to the first manned lunar landing site increased, more people started setting up shop until by the beginning of 2012 a sizable town had grown up around the park.
Port Luna is unique in that it is the only major Fen settlement considered to be part of a mundane nation. The United States maintains territorial control over the city as part of the agreement ceding Tranquility Base to the Parks Service. All residents of Port Luna are considered to be either US citizens or resident aliens -- though the Coast Guard's lack of resources means that checking visa status is sporadic at best.
Outside of Tranquility Base, Port Luna's greatest claim to fame is that it was the site of the November 2009 Tomed Incident, the bar-brawl-turned-riot that still stands as the largest and most violent interfactional dispute in Fenspace's history.
The city of Port Luna is organized in rings. The Inner Ring (also known as Ring 1) is the oldest part of the city and consists of government buildings and the more expensive apartment buildings. All the buildings in this ring overlook the park. City/territorial government is located in the Armstrong Building (Ring 1 southeast). The park entrance is in the west sector of Ring 1.
Ring 2 is the commercial center, focusing on the tourist trade in and around the park. Most of the hotels in Port Luna can be found in this area. Collins Communications operates the lunar interwave subnetwork out of their offices in Ring 2 East, and the Convention Authority (the permanent office of the Fenspace Convention) is in Ring 2 South.
Rings 3 and 4 are the main residential sectors of the city. Most of the people who live full-time in Port Luna (and can't afford housing in the Inner Ring) live here. Ring 4 is also home to some of the finer entertainment establishments in town, such as the Tranquility Drafthouse (four stars in the Fenspace Travel Guide).
Port Luna International Spaceport is not connected to the ring structure, instead sitting several kilometers away to the north of the city. Access to and from the spaceport is managed by the Lunatrak rail line, which runs overland in a pressurized tunnel from the spaceport to the city's main transit hub in Ring 2.