How to find all nonlinked subsites of a web page?

Is there any way, to find all subsites of a site? Even those, which are not referenced by this site. For example: I have site www.foofoo.de, this site has 3 subsites - www.foofoo.de/horse, www.foofoo.de/dog, www.foofoo.de/mouse. Site www.foofoo.de has links to /horse and /dog but not to /mouse. However i can still visit site www.foofoo.de/mouse if I specifficaly write this adress to my web browser. Is there any way, I can find this subsite if I dont know it's complete adress, just www.foofoo.de? Thanks