If you feel crafty and would lie to make some easy and cheap greek style columns, check out this thread for a step by step guide.

For the base and also the top of the non broken columns you will need some squares and circles of an even thickness. I made these out of XPS foam, then textured them shaking in a jar full of coarse sand. You can also use a ball of aluminium foil and press it all over the foam.

Once you have all the foam pieces you need, glue them together and make sure they are properly aligned. PVA glue allows you to correct the alignment and get a very strong bond. For the bases you can also keep them in place with a screw, that will add weight for stability.

For the actual pillars, all you need is some corrugated cardboard peeled on one side. Decide how tall and wide you want yours and cut rectangles of the peeled carboard. Then glue one end to the other with just a little PVA glue to get a cilider, making sure you hide the seam.

I recommend cutting whole pillars at this point to make two broken ones with ease. Glue them to the heavy bases with a bit of PVA. Make sure you safe the bases without a screw for the top of the unbroken columns. Once dried I added some coarse sand and a dab of PVA to lock it.

After drying overnight I filled the broken columns with some paper and then added some filler (the one for repair scratches and little holes from walls) for the broken surface. Once the filler dries a bit, you can texture it a bit so it doesn't look too smooth.