Home made beardie cage

what are the shelvings or rock formations made of?

The rock is styrofoam covered with tile grout. I got the polystyrene in 2x4 sheets and used three bags of grout to cover it all. The expensive part is the non-toxic sealant for the grout. I got everything at Lowes, and haven't had any problems with the cage or lizards. Also, I used liquid nails to glue it all together. Make sure you get the one for polystyrene(It's got a blue label). My web site has more detailed info(see profile)

how big is the tank?
and how long did it take to make it?

This is made from the pre-cut 2x4 ft plywood that is available at hardware stores (like Lowes). The bottom is 3/4 inch 2ft by 4ft, the back is 1/2 inch 2ft by 4ft, and the sides are both 1/2 inch 2ft by 2ft. I had to cut a little on the sides for it to fit together square. I think that I spent about a week building this one. I am working on another cage now, and it is taking longer because I am not as motivated. I think that you can rough-in the box and glue the styrofoam in a day, and probably start on the grout(depending on how complex it is). Be sure to let the grout dry completely and then let the sealant dry and air out completely.