Question about trenches

[Huib Versloot]

No not about CS trenches but about real trenches.
Yesterday I visited the trenches I recently discovered with Google Earth. I noticed that some trenches have a circle at the end with an elevation in the centre of the circle. I figured that this was done to place an Heavy MG (MG 42 tripod or something) on the "elevation" and by the possibility to walk around the "elevation" the MG could fire towards all sides quickly.
I was never in the army (to my regret now)but I'm sure there are people here who can tell if my assumption is correct. Attached are photos of these trenches.

Thanks
Huib