multiple sublistings in natural Google

Some sites have several sublistings under their natural result

[Stronkie]

How/Why does this happen?

I often see a listing with a sub listing in Google, but this listing for a travel site is showing the main listing with no less than FOUR sublistings which are very product orientated displayed like this:

MAIN GOOGLE LISTING (link)
Description
URL
Flights (link)
Special Offers (link)
Holiday Extras (link)
Contact Us (link)