Intercepting higher neighboring plots: L-shaped stones, etc. - Tips

Then the neighbor has already built the retaining wall?

Or are you doing underpinning?

Yes and no, this is one of 4 neighboring plots and yes, we would have to support the wall because we will go down another 70 cm, to the base of the current wall. All other plots of the other neighbors running lengthwise are only about 30 cm as high as the wall.

I will try to take a photo around midday today.

What speaks against a steep planted slope. 1:2 definitely works, then you lose 1.5 m of horizontal area. Is the space so tight? If necessary, a natural stone wall in front of it. 70 cm is no longer 1.5 m.

We would have to support the wall because we are going 70cm deeper again

Phew, when I look at the photo and assume that the fence on the wall is a standard 80cm wooden fence, then the wall underneath must be just about one meter high. Adding another 70 cm height difference, you would need 2.05 meters of L-shaped stones to achieve this even with minimal soil coverage. That’s a small fortune buried, only to end up looking at a concrete wall that is 1.7 meters high with an 80 cm wooden fence on top. That’s not a nice sight. And it will take years for it to become overgrown. I would seriously consider - for cost reasons and for a more pleasant appearance - a slope with attractive planting. And one more thing: How close are the houses to each other? If the neighbors all around live at a higher level, that always looks strange - and I don’t want everyone looking at my dining table from their window saying “Look, Horst, there’s fish next door again!” No, I wouldn’t want that either.

I honestly see very little of the described problem in the picture!

and yes, we would have to support the wall because we are going 70cm deeper, to the base of the current wall.

Are you still below the existing wall? Are you digging it out or how is that happening? You can't just expose the wall?! Or is it already floating higher than you are?
Sorry, but I don't understand it.
If everyone has this slope, basically perpendicular to your house, then you level your garden up to your higher-lying area and undermine their existing L-stone. Correct me if I’m wrong!
In my eyes, that is the beginning of the end for the higher property. Then you have two walls lying one above the other... won’t they collapse?! Or am I wrong here?

Sort of, this is one of 4 neighboring properties

How have the others solved it? How wide is the property you have?
I would put a raised bed or terrace bed in front of it – there are definitely worse things, like a high concrete wall!

All correct, in parts ;). The photo presents the "anti-example." As described, the gardens to the right and left, running lengthwise to our property, are not so massively built up. One neighbor only did this to level his entire garden. It is always the rear boundary of the neighboring properties. The neighbors' houses stand about 1.5 m higher at about 20 m distance from the boundary. Since the entire area slopes down towards a distant ditch, it is all hillside and results in this strange topography.

With the neighbor with the wall, I am already considering simply filling in this area since our new garage runs 1.1 m away from the property line. Then I save myself elaborate slope stabilization. The garage would then practically be a retaining wall for his garden.

A slope is one option but of course limits the possible depth of my property and then slopes down to the lower house. I don't find that quite so nice, however, and that needs to be seen after a rough profiling, I don't want to drink my coffee in a concrete enclosure.