Could a bolt this size actually be used on a project?

From my location it appears the image is broken, however I can assume with my imagination and the comments it’s a pretty big bolt.

Exceptionally large bolts are surprisingly not that uncommon. They often show up in oil industry to bolt flanges and for use in huge structures. But they are usually custom low production bolts designed for a specific use case and not mass manufactured. M180 is the largest I’ve ever seen in a bolt list to purchase from a supplier.

24” nuts was “common” for a time, however this has mostly changed to higher quality smaller diametre alloys and bolts.

At one point there were 98” diametre, and nearly 30’ long bolts made in the 60s

Penrith Engineering Works in Clydesdale Scotland in 1967. The bolts measured 27' 4" long each and had a diameter of 4' 2".

As far as i remember it was an experiment to bolt oil tankers together that failed miserably.

As mentioned in the oil industry it is common to use large diametre bolts, as much as 20” (w510) can be “easily” purchased from ITH for example.

There are of course large problems with large bolts (fitting, yes?) handling, manufacturing, weight, transportation, actually bolting them, etc etc And often when the design requires such large bolts then one will generally choose a different (permanent) connection method.