The Exo Terra Reptile Den allows easy observation of reptiles and amphibians while in their hiding and sleeping spot without opening the terrarium and disturbing the animals. The unique "through the glass" magnetic rock formation allows monitoring without disruption and eliminates stress during observation. The rock cover can be removed from the outside of the terrarium for observation. The two pieces are held together through the glass by strong magnets. The rock is insulated to keep the tunnel system cooler than the ambient temperature inside the terrarium. Perfect nesting site for various species.