I hope you are stacking it, in tank.
It's nearly impossible to move a structure say from a tabletop into your tank and get the same structure.
While building your structure, Think from the very bottom layer about creating caverns and through ways for fish to swim and water to flow. Build from the base layer, which is your footprint, and build vertically. Every step of the way, consider how you can orient the rocks to get the best fish habitat and flow through. As you get to the rocks that will be your viewing and mounting surface, Take that into consideration as well.
Building a scape is not a fast thing.
@F i s h y and I spent probably 8 hours obsessing over the initial scape for my 300.