Mars One was the second sandbag structure built at CalEarth in the early 1990s using individual 50lb rice bags filled with sand (unstabilized) and rows of barbed wire. In 1984 Nader Khalili presented at a NASA symposium for lunar and martian construction, sharing his ideas of both ceramic style architecture as well as "velcro adobe" which later became the SuperAdobe building system. Mars One was a prototype for a lunar/martian colony design, and includes a handmade skylight and a small sitting nook as well as a fireplace. Mars One was also the first structure to include "reptiling" plaster, the small earthen balls used to cover the exterior of the building providing an extra layer of protection and eliminating smooth surfaces prone to cracking. Just like many of the buildings at CalEarth, this structure has been left in its original form to observe and research over time. 

Note the Nubian-style arch used to support the solar-facing window. Later, domes on-site did not keep this feature, as it captures too much summer desert sun! It may be an excellent feature for cold-climate domes.