Assertion: fortress's tower | /r/HasProperty | immune to tunnelling under the tower
Facets:
value: under the tower
type: LOCATION
value: due to the absence of any corners
type: CAUSE
value: relatively
type: DEGREE
value: unlike the square shaped towers
type: OTHER
Source sentences:
text: Another feature of primary importance was that, unlike the square shaped towers, round towers were relatively immune to tunnelling under the tower due to the absence of any corners required for tunnelling.