Small Retaining Wall Need Concrete Ideas To Make A Small Retaining Wall For A Small Garden?

Need concrete ideas to make a small retaining wall for a small garden? - small retaining wall

I want concrete square or rectangular
Protruding parts of the earth, where it could be a little land for the garden to a level
My area of the garden that receives plenty of rain, and I wish that the fight against floods by construction of a wall on 3 sides and leave the empty container is open downwards
I would appreciate any information they could provide a form or any kind of concrete, the use of his hands could use could use
I once heard that hay can be mixed with cement in a manner
I like my garden a natural look and appearance of the old, if possible