TERRARIUM :: Inside (left to right): a miniature guzmania bromeliad; maidenhair fern & selaginella (a type of spikemoss or 'fern ally'--not true ferns); & a mix of selaginella, button fern & variegated Dizygothecae (often has green foliage & plum hues).
Disney world does this! Lowes sells the 4 to 6" round PVC pipe with holes already drilled. Purchase an end cap, fill with rock, soil, and plant. I will often put these in the center of a very large pot to stabilize, and add amazing height and color to a container that has trailing plants (no end cap or rock needed if you are placing in a container)