I see photos on Zoochat that say, "*Animal* Grotto", and all it is is an exhibit surrounded by a tall, fake/real rock wall. A grotto by definition is a cave-like structure or a cave itself, not a rock wall surrounding an area. Sure there is a cave most likely in those exhibits people call grottoes, but it isn't one big cave in general. I'm just curious as to why people call them that. Here are some examples.
http://www.zoochat.com/39/african-wild-dog-exhibit-279241/
http://www.zoochat.com/556/jul-2012-american-black-bear-exhibit-280043/
http://www.zoochat.com/1115/porcupine-grotto-279433/
http://www.zoochat.com/562/grizzly-bear-exhibit-detroit-zoo-42074/
http://www.zoochat.com/545/sloth-bear-exhibit-274509/
http://www.zoochat.com/597/empty-bear-grotto-273934/
http://www.zoochat.com/562/detroit-zoo-2003-bear-grotto-136839/
http://www.zoochat.com/622/sun-bear-exhibit-199709/ (I am shocked people call this an outdated exhibit)
http://www.zoochat.com/1128/giant-anteater-white-nosed-coati-exhibit-242984/
http://www.zoochat.com/549/polar-bear-pit-175356/
http://www.zoochat.com/39/african-wild-dog-exhibit-279241/
http://www.zoochat.com/556/jul-2012-american-black-bear-exhibit-280043/
http://www.zoochat.com/1115/porcupine-grotto-279433/
http://www.zoochat.com/562/grizzly-bear-exhibit-detroit-zoo-42074/
http://www.zoochat.com/545/sloth-bear-exhibit-274509/
http://www.zoochat.com/597/empty-bear-grotto-273934/
http://www.zoochat.com/562/detroit-zoo-2003-bear-grotto-136839/
http://www.zoochat.com/622/sun-bear-exhibit-199709/ (I am shocked people call this an outdated exhibit)
http://www.zoochat.com/1128/giant-anteater-white-nosed-coati-exhibit-242984/
http://www.zoochat.com/549/polar-bear-pit-175356/