There can be few simpler ways to tick off as many countries as possible than by boarding a world cruise.

The longest of the nine we've unearthed - a 180-night voyage on board Insignia, operated by Oceania Cruises - visits a truly remarkable 90 ports and 44 countries. That's more than a fifth of the world - not bad for a six-month trip.

Scroll through the graphic above to see exactly where the longest cruises go.

See a fifth of the globe on the world's longest cruise

While the cost of a world cruise might seem an awful lot - the cheapest on our list is £10,399pp (for 115 nights) - it can represent good value for money, particularly if you're used to paying London rents.

Earlier this year, Telegraph Travel worked out that living on a cruise ship can be cheaper than living in the capital. We used the example of a 91-night trip, which was available at the time through Cruise and Maritime Voyages for £4,387.

That bill was £650 less than a 13-week stint in London, based on the average rent (£268 a week = £3,484) plus council tax (£235), energy bills (£159), water bill (£92.50), food costs (£650) and transport costs (£417.30).

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