Just purchased a late 1800s house. There is a 4 inch wide concrete berm that runs the width of the yard and just stops (see in the attached picture running just left of the patio set). The yard and surrounding area is very flat and the berm has a short ~3 inch drop off on the side nearest the house. I haven't dug around it yet to determine how deep it goes. I would like to remove it but I'm not certain what it is. My guess is that there used to be a garden in the back and this marked its edge.
Anyone encounter this before? Is it okay to take it out?