I was inspired by severy other posters on this board. They made it sound so easy I had to try it--Drako's tank was so big and empty...
I measured the top tank opening to make sure that what ever I made would fit...VERY important.
I took some plywood scraps and formed the back as well as the shelves/ledges. I used angle brackets and screws to fasten the pieces together. I also used a small piece of plywood for a "leg" for support (very right bottom of my rock wall)
I purchased a sheet of 1 in styrofoam and used liquid nails (the one labeled safe for styrofoam) to assemble the pieces. I used small pieces to "sculpt" the edges and also stacked pieces together for the steps and cave support.
Once assembled I used some spray on foam--used for filling cracks--to fill in gaps and add texture.
I used gloves and my hands to apply several thin coats of a nutmeg colored tile grout to all sides of the rock wall. I let it dry overnight between layers. I then let it set for a few days to "cure" before I applied the sealer. A few more days and Drako had his new home. He basks on the top ledge and usually spends most of the day on the middle level. In the evening he crawls into the cave to sleep...most mornings he can be found HANGING from the top ledge (over the stairs)--quite funny looking.
HTH
I'm sure you can find other more complete directions in other parts of Kingsnake...
DM