This is a scratch-build base that is currently in a state of preparation. As can be guessed by the size, this base is going to be for a dreadnought. A contemptor dreadnought to be precise.
The circular base is a standard citadel miniature base. On top of this, I've added a pair of parts from the floor of the Imperial Ruins sets -- both a flat grill plate, and one of the sides with a sharp peak on the end.
Underneath the main plate, I've built five pipes from hollow plastic tubes, arranged with three on the bottom and two on the top. I plan to push some other material through these eventually - perhaps some wires, or maybe even modelling some effluent coming out of them. The pipes are surrounded by a milliput build to keep the platform stable and add some weight to it - largely as a counter-balance for the dreadnought I plan to place on to. Finally, there's some plastic grid that I've added over the pipes and to one side of them.
The contemptor will be added in a dynamic pose, striding up the step to the top of the platform with one foot on top of the pipework seen to the bottom of the image.
There's still plenty more work to get done on this scenic base, but the basis is now there and I can now proceed with posing the dreadnought on top of it.