Assertion: city's wall | /r/MadeOf | massive stone blocks
Facets:
value: usually
type: TEMPORAL
Source sentences:
text: Between the two levels, the retaining walls, usually made of massive stone blocks, are decorated with the great iron rings once used to moor merchant vessels, and some are pierced by openings left by water gates for old palaces or inspection ports for subways, sewers, and underpasses.