St. Ninian's was an old church located down the road, to the southwest of Redwall Abbey.
The building's origins are a bit hazy. According to a popular legend, the family of a Mossflower mouse named Ninian had grown too large for their abode, so Ninian decided to build a new home for them. However, he was so lazy that his wife performed most of the construction, prompting her to erect a sign saying "This Ain't Ninian's!". Generations of weathering eventually faded off the first three letters and the exclamation point, making the sign read "Saint Ninian's"; this reportedly caused the building, when it was rediscovered, to be mistaken for a church.
Over the seasons, the oft-abandoned building was used by several families and groups as a home, until Cluny the Scourge evicted a family of mice from it and set up his army's headquarters there. From that point on, the building was dwelt in by a succession of vermin bands, the last being a group of jackdaws during the time of Abbot Durral.
When the birds killed Piknim and badly wounded Gerul, Tansy, and Craklyn, the recorder Rollo ordered Saint Ninian's to be immolated, asserting it was no longer anything but a place of evil. Skipper, Rangapaw, and the ottercrew drove out the jackdaws and set the building aflame, monitoring it to make sure it burned completely to the ground. It has not appeared, nor has it been mentioned, since its destruction.