DIY One-man Grease Pit

This was the best low-budget DIY project ever. It just took a lot of effort but all the materials were left-overs from other works during renovations. The thought of "who was here when these earth layers were formed" kept me very busy, because you can clearly see how nature formed them, but how long ago was this?
The ventilation is obviously for safety and was switched with the lights. During building I came up with the idea to have a little niche to put my tools into while working.
Once finished other works on cars and our campervan became so much easier. I'm considering to build one again, but then longer with a side entry.