I came across this site awhile ago and made one for my rabbit. It is a hidey house made out of a storage tub. He really loves it and it fits nicely in a corner of his condo. It is especially handy when noisy vistitors come over and he wants to hide, or for a cozy napping place. It could be easily modified for guinea pigs, and it's big enough so that multiple piggies could snuggle together. If you made one for piggies I would use towels, fleece, or bedding instead of the carpet.
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