Need suggestions for finishing drain
We had a drainage system engineered for our property. It's been installed for about a year. Our landscaping contractor threw some mulch around these drains (they're about one foot square) but they look ugly. The drains are both below grade (the one in the photo is actually higher than the second one). They came in handy in December during a massive rain storm. If we hadn't clean the leaves off the drain we would have had flooding. But that kind of storm happens once every 5 years.
My questions are:
1) I'd like to plant around them but I feel like i need to retain the dirt somehow...mini retaining wall? what material should i use?
2) Can I / should I place a few large river rock on top?
3) what's the most simple/elegant /natural way to make this look finished or better yet - make these disappear? thanks!