Good old wiki. Yes, this is a possibility. Tectonic plate shifting can supposedly cause pyramid-like hills covered in pudding stone which can give the appearance of being man made. Aerial shots of the structure however don't leave me with the feeling it is natural.

Electromagnetic tests at the top of the pyramid prove there is something going on in there. And the scans show a chamber. In both Bosnia & Java. Then there are the healing aspects of the tunnels under the Bosnian pyramid of the sun. The health benefits of entering these tunnels are observable and being independently reported on by those who go there.

Something else to think about is the way in which the ancients could carve their pyramids out of existing mountains. All evidence is pointing towards this at Gunung Padang.