SHELF or triangular shelf is a modular system that allows you to sculpt armies of triangles into any form you like. You can vary widths, lengths and depths, plus go on to snake these sculpture-like forms across walls or floors.
Don't have much space to grow your favorite plants? Try building a vertical garden like this one, designed by Susie Frazier. Using salvaged wood, threaded rods and bolts, and a handful of mason jars, you can construct a simple hanging planter to add a lot
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.
Gabion stone wall at Maleny House in Australia. Designed by Bark Design Architects. This could be great if you left space in the top for a planter or planted right into the sides with moss, air plants, or tiny hidden sculptures.