Mars City
The Main goal of Elon Musk and of SpaceX is to establish a self sustaining civilisation on Mars.
Elon MUSK quotes:
"Now is the first time in the history of Earth that the window is open, where it's possible for us to extend life to another planet,"
"That window may be open for a long time — and hopefully it is — but it also may be open for a short time,"
"I think the wise move is to make life multiplanetary while we can."
Colonising Mars has long been a passion of Musk's. Indeed, the entrepreneur has repeatedly said that he founded SpaceX in 2002 primarily to help make humanity a multiplanet species. Having a self-sustaining outpost on the Red Planet would serve as an insurance policy, making humanity's extinction unlikely even if something goes terribly awry here on Earth.
Colonising Mars would have other benefits as well, he added; the effort would greatly advance science discoveries and technological capabilities, and it would help inspire and excite people from all walks of life and from all around the globe.
Mars settlement "would be a great adventure," Musk said. "There need to be things that people look forward to when we wake up in the morning."
Mars Base Alpha
In Elon Musk presentation in 2017 he showed a series of slides for Mars Base Alpha growth, but they appear to be unrealistic concept art.
SpaceX Mars base
Mars base 2025
Mars Base 2025
The First landed Mars astronauts, the base will consist of 4 cargo BFS and two human spaceships, the initial accommodation will remain in the BFS while offices and operation quarters are built into the surface terrain using automated machinery. The picture shows production plants and solar arrays and airlocked entrance into a vehicle assembly and maintenance facility also built into the terrain, mirrors could be used to reflect sunlight into the structures.
3D printers will be used to produce items from in-situ refined resources.
The initial structures will be mined out and the spoils used to make bricks etc Ideal for Elon Musk's 'Boring Company'.
A very important urgent first steps will be the Oxygen, Water and fuel operations and supplies, followed by hydroponic food production underground from radiation receiving reflected sunlight from mirrors.
Automated and manned Vehicles on Mars will be Electric and shipped from Earth for some time in the foreseeable future again built using Elon Musk's 'Tesla' electric autonomous technologies.
More advanced manufacturing for items like Solar panels and copper wires, copper ore locations will need to located dug up, most likely requiring some sort of Nuclear power plant, SpaceX is currently(2018) trying to obtain Nuclear materials to do the research required that also might one day lead to breakthroughs into safe nuclear propulsion systems for getting to Mars faster.
Communications
Good communications between each person on Mars will be essential, this again where one of Elon's Companies will help with on orbit satellites, as the low density in Mars atmosphere will help for the communications satellites to work at lower Mars orbits without decay that a LEO satellite suffers from, also a Mars GPS system could be in orbit as well. Mars and Earth lagrange points could provide for continuous Earth/Mars high bandwidth communications.