The Kitty Hollow is a series of trees for: climbing in or on; running through it or on it; hiding on the in-side shelves or lounging and sunning on the out-side shelves. This tree is PURR-FECT!! The Kitty Hollow is 12" in diameter. The 48" comes with a base and top that are 20"x20". There is an entrance to the tree located at the base of all the trees. It is located in the back of the tree, you know, a secret entrance. There is also an inside shelf to make it easy to get to the top. The top of the tree has a nice rolled edge on three sides to snuggle up against. The top is solid there is no exit hole on the top this gives a much larger surface for lounging and sunning. Assembly required. Colors are Factory select Brown Base, Beige Trunk and Green Leaf and top. Factory Select Colors may vary from colors pictured.