cyclopean

cyclopean \sahy-kluh-PEE-uhn, sahy-KLOP-ee-uhn\, adjective:

1. (sometimes lowercase) gigantic; vast.
2. of or characteristic of the Cyclops.
3. (usually lowercase) Architecture, Building Trades. formed with or containing large, undressed stones fitted closely together without the use of mortar: a cyclopean wall.

Together in this greater self they felt the headway of the long, low hull, the prodigious heart glow of the hungry fires, the cyclopeanpush of steam in eight vast boilers, the pulsing click and travail of the engines...
-- George Washington Cable, Gideon's Band, 1915

On his return, he threw himself into the cyclopean labour of clearing, ploughing and planting the virgin territory he'd inherited; it was in the far south-west of the island, an area known as Terrenos de Sio Miguel.
-- Miguel Sousa Tavares, Equator, 2009

Cyclopean refers to the mythical Greek creature Cyclops, a kind of giant who has one large eye in the middle of its face. This adjective has been used to mean "gigantic" since it entered English in the 1600s.