One idea that's often floated when discussing ways of constructing martian habitats is that of "doming" over small craters or valleys and pressurizing the whole area. This would have several advantages such as having a large open space for scientists/colonists to spend time out of their spacesuit and protecting the people from the harsh conditions on the surface. One problem that this presents though is that underneath a transparent dome the people would be exposed to more radiation from the sun and cosmic background radiation.
Question: What would be the most effective building material that is transparent, easy to obtain on mars, and protects the people inside from radiation and other martian dangers?
My idea: Glass can be produced on Mars with the abundant silica deposits and reinforced with layers of plastic brought from earth. Then, these glass panels are cut into triangular shapes and two geodesic dome structures are built inside each other. The space in between these two domes is filled with water providing an excellent radiation shield and automatically "repairing" any punctures or cracks due to micrometeorite impacts by freezing upon contact with the martian atmosphere. Water is either insulated so it doesn't freeze inside the dome or is actively heated (maybe as coolant for a nuclear reactor).