Building Underground Hibernacula

Today i decided to re-furbish one of my outdoor vivaria for when the weather warms......when ever that will be.This particular viv has dimensions of 2m long x 2m high x 1m deep and is of an aluminium frame fixed to a gravel board base.
The viv is glazed with acrylic on sides and roof, but the front is 50/50 acrylic and mesh, which gives the reptiles good access to natural sunlight and allows good airflow.

These greenhouse type structures can get very hot in Summer and cold in Winter, so underground chambers need to be built in to give the reps refuges/hibernacula.

One chamber is made from bricks with a paving slab on top which should keep cool in the Summer months. The other is a poly box which will keep at a fairly constant temperature throughout the year.

A tunnel is then attached to the polybox, which the lizards can access from the surface.

The poly box is then covered with wood or a slab to protect it from damage and the whole area is covered with a 75-100mm of a sand/soil mix.
Then various logs and stones can be placed on top for effect and basking/climbing spots for the reptiles.

I then added some large upright logs for access to the upper reaches of the vivarium, climbing plants will be grown up these. Other plants will be added over the coming weeks and maybe a few more logs/rocks.