I often mention rabbit dart holes. By nature rabbits need to hide and quickly sometimes. They often choose small spaces - and these spaces can be cosy in winter. Two rabbits can warm up a space whereas larger areas tend to stay cooler. I would wish to choose my preferred temperature. I compare it to sitting snug by the fire at night while the other corner of the room is pleasantly cool if needed.
Yesterday I wished to make a cosy bolt hole to be used in the Watch Tower Plus and thought the den dig would do the job. It could be stuffed with straw and hay (maybe soil) and provide a hiding place to snuggle into.
Slightly larger, the Hay Hutch provides a roomier enclosed snug and the Top Box a raised insulated snug space.
Interestingly, when we tried our group of 4 rabbits in an enlarged Top Box they only ever sat in half of it making the doubling in size unnecessary. The bunnies like to share this space or sometimes split across a couple of cosy areas.
Underground the rabbits move between 'rooms' or chambers and there is always the option of exiting from at least 2 directions. Like us, they probably want to be with company at times but if falling out occurs they can move on. The more I watch rabbits the more they reflect our social scene where we are equally fussy about who is there!
To enable all this natural behaviour we just need to offer warmth, fresh air, sun or shade and imagine what we would like for ourselves. We can never assume to know what is ideal for another species but giving options is one way to allow them to choose and keep them happier and healthier through it.