Does anyone have a creative/safe way to hide this hideous sewer vent and manhole?
Thanks in advance!
That concrete riser really should be buried, ideally. So give the idea of dumping a lot of dirt there some serious thought.
Disguising the pipe (and the riser if you don't bury it) has many possible methods, starting at the low end with painting it, since sewer-pipe green stands out quite a bit. As is, you might make the pair resemble a broken-off stump with a branch sticking up using brown/gray/black paints.
Presumably you don't want tree roots right there, but some artificial foliage might help, or some annual vines trained on strings. Going more involved, you put a (removable) windmill or lighthouse (or other decorative motif structure) over them.
As someone who is currently living my first Septic home, I would have identified this photo as septic (not sewer- sewer connects to your house underground with pipe from the street) especially with it being downhill and away from the house. I concur that the majority of the cemented portion showing would generally be buried, check the age of the septic- the surrounding dirt may have simply eroded over time. (You should have a septic inspection separate from your general home inspection)
As far as "hiding" it... providing it is indeed septic, there are some things to know. First, you need to find out where your drainage field is, because you cannot build or plant anything significant in that area. The ground is, for practical purposes, hollow in that area and it can't hold the weight of any structures or large root systems. Second, whatever you Do decide to install needs to still allow access to the cap. (the man hole looking part) Think in similar terms to hiding an A/C unit. This is for future maintenance and in case of problems with the unit. Last on my list is that you plan for those who will be around it most often. Do you have kids? Then it should be kid friendly. Is the yard person the only one going near it most days? They need to be able to clearly see the cap from the mower. These sorts of considerations can make or break a project.
It's possible you could fix this with some grass, wildflowers (no deep roots), and a conveniently placed windmill, or you may be more interested in some raised beds, or a vertical garden, or even a mini shed. That part is all up to you. :)