BIG starship comparison poster (careful what you click for)

[LongBlade]

OK, found the previous book, Priests of Mars.

Will quote from pages 37-38:

A passing battleship that Roboute regocnised as a Dominator-class vessel sailed below the Speranza, and its length wsa more than eclipsed by the beam of the Ark Mechanicus. Where the Navy's ships tended towards wedge-shaped prows and giant cathedrals of stone carved into the craggy structure of their hulls, the Mechanicus favoured a less ostentatious approach to the design oft heir ships. Function, not form or glorification, was the guiding light of the ancietn Mechanicus shipwrights. The colossal vessel had little symmetry, no gilded arches of lofty architecture, no processional cloisters of statuary, no vaulted, geodesic domes and no great eagle-wings or sweeping crenellations.

The Speranza was all infrastructure and industry, a hive's worth of manufactories, refineries, crackling power plants and kilometre upon kilometre of laboratories, testing ranges, chemical vats and gene-bays, arranged in as efficient a way as the ancient plans for its construction had allowed. Its engines were larger than most starships' full mass, its individual void generators and the Geller arrays large enough to shroud a frigate by themselves.

Roboute had seen his fair share of space-faring leviathans, some Imperial, some not, but he had yet to see anything to match the sheer bloody-mindedness and ambition of the Mechanicus to have built such a damnably impressive vessel.

We never get a true idea of how large it is, but it not only carries a legion of titans but has facilities to repair and create them.

[Staggerwing]

So, quite a few 'X's before the 'L' then.

I found this artist's interpretation at the WH40K wiki: