- their siting, overlooking the st lawrence and charles river, strategic points in the city's historic defences;
- their squat, cylindrical, two-storey massing with slightly inclined exterior walls;
- their rubble masonry construction with sandstone ashlar exterior facing;
- those elements typical to martello tower design, including their tubular massing, circular interior compartments, their thicker walls facing away from the city, the interiors? solid masonry pillars that support bombproof arches capped by thick masonry, the gun platforms at the top of the towers, the encircling stone parapets at the top of the walls, the high entrance and embrasures at second storey level, the small bombproof magazine in the basement;
- the depressed, circular walkway within the parapet of tower no. 2 which permitted simultaneous fire from both the soldiers and the artillery situated on the gun platform behind;
- the surviving original materials and finishes, both exterior and interior;
- the integrity of the spatial and strategic characteristics of the towers with respect to each other and to the other elements of the city's defence system;
- their relation to the surviving strategic viewscapes.
