Gabion walls don't need any kind of drains because they are porous throughout. Gabions can be customized to make them more useful in public spaces. Gabions can be filled with any heavy material--diverse stones, metal artifacts, obtanium, etc.
Hot water tank heated by wood burning stove. From Teach Nollaig, Tiny house in Ireland. Could be improved by adding a small sterling engine to power a circulation pump, allowing the hot water tank to be up higher [improving pressure]. Also INSULATION!