Like many current-day megacorps, I suspect it is a diversified company, with branches in many different fields and locations.
An example from the last century is Krupp... Primarily a steel manufacturer, they were started in 1587 when Arndt Krupp (a trader in Essen, Germany) purchased a large number of "gardens & pastures" from the families of victims of the bubonic plague.
His son married the daughter of a gunsmith, and joined his in-law's business.
By a little over 300 years later, Krupp produced rails and rolling stock*, household goods, cannon, guns, ships, machinery of all sorts, and mined their own coal & iron (from mines throughout Europe, Scandanavia, and into Africa). It ran chemical laboratories and financed inventors... Rudolf Diesel got the money (and facilities) to perfect the diesel engine from Krupp.
In the company-built (and owned) towns for its 43,000+ (1890) workers, Krupp owned & ran a police force, fire department, schools, hospitals, retirement homes, a separate telephone system linked into the national grid, and all industries needed to feed, clothe, etc. those workers & their families... all staffed by Krupp employees.
* Despite their justifiable reputation as arms manufacturers, Krupp's first product to see large-scale success, and the one which catapulted them into the forefront of the world's steel manufacturers (and paid for their large-scale tooling-up for arms manufacturer) was wheels & axles for rail cars... first displayed at the 1854 Munich Industrial Fair, the stunning success of which (15,000 per year by 1860) is commemorated in their corporate symbol of 3 interlocked circles (wheels).
Someone from another country who encountered Krupp in one of those other guises might think that that is all they did, but they would be wrong.
After all, that's why they call them "Mega-Corps".
