Discover one of only four blockhouses built on the Rideau Canal. This building features thick walls designed to withstand small cannon fire and a tin sheathed roof to defy torching. Situated on a knoll to observe the lock and channel, the blockhouse can hold a 20-man garrison and house the lockmaster. As part of Digital Doors Open, enjoy the documentary short below by Allison Margot Smith recounting the challenges posed at The Isthmus — now the Newboro Lock where the blockhouse is located — during construction of the Rideau Canal. Its construction cost a great deal, not only in terms of money, but also in lives and time. Colonel John By, however, employed an unusual method — The Big Breakthrough — to drastically reduce these losses by using a slack water canal design that today defines the heritage value of this UNESCO-designated waterway. (Photo: Rosanne Lake)