As a result of the thinning and receding Arctic ice, one such journey, the Northwest Passage, has become more and more accessible (although there is still no guarantee you will get through; indeed, one ship had to turn back only last summer).

More recently, we have seen the very first approval from the Russian authorities for a western passenger ship to attempt the Northeast Passage, with Hapag-Lloyd's now retired Hanseatic (ice-strengthened but not an icebreaker) making the first journey in 2014.

The search for these polar routes was key to trade in the days of the great explorers - imagine the time and money you might save, journeying from the Atlantic to the Pacific and vice versa, when your only alternative was to go southwards to the treacherous waters around Cape Horn. Early explorers were trying to assess whether there was indeed a sea passage, or whether land bridges would prevent such a journey.

Now that citizen explorers have the option to take one or the other (or indeed both!), how would you choose between the two?

The Northeast Passage, known by the Russians as the northern sea route, is the journey eastbound from Norway to Alaska or vice versa, to the north of the Russian land mass. In the 17th century it was established that there was indeed a sea passage, and Vitus Bering's successful 18th century explorations were part of a larger scheme of Peter the Great, known as the Great Northern Expedition.

The Northwest Passage is the sea route westwards from Greenland or Newfoundland to Alaska, or vice versa, via waterways through the Canadian Arctic archipelago. For centuries, European explorers had been seeking a navigable route, but the first complete passage was not made until Norwegian Roald Amundsen's expedition of 1903-1906.

From a cultural point of view, therefore, you are choosing between explorations of Russian Folklore, Chuckchi and Inuit bone carvings, and a Paleo-Eskimo camp dating back 3,400 years (Northeast Passage); or of small towns and villages with a fascinating mix of indigenous and Danish or Canadian culture (Northwest Passage). Emblematic sites of Franklin's and Amundsen's attempts to master the Northwest Passage will stand out, whereas those travelling the Northeast Passage will be focussed on more recent history, with Soviet military bases and nuclear installations.

As for wildlife, of course everyone on either journey will be looking out for polar bears, and on Hanseatic's first journey through the Northeast Passage an extraordinary 86 bears were spotted. On this journey, you will have the opportunity to sail to the edge of the ice, looking out all the time for birds and sea life. On the Northwest Passage bear sightings are unlikely to be so frequent, but you might see narwhal in the water, and such a sighting is less likely in Russian waters.

Image Credit: ©Silversea Cruises Ltd.

Overall, however, the wildlife will be similar: on land, you can expect to see musk oxen, reindeer, and Arctic hare. In the ocean, look out for walrus, a whole range of seals, and humpback, bowhead and beluga whales. In the air, you'll see rather more species of sea bird on the Northeast Passage, and of land bird on the Northwest Passage.

Scenery, as you get away from the sparse settlements, will in both cases be stunning, a true wilderness: tundra, glaciers, a sprinkling of summer colour, sheer cliffs and waters clogged with growlers and bergy bits. Aurora sightings are possible, and the extraordinary colour palette of all manner of black, grey, blue and white feels literally 'out of this world'.

Cruise lines offering these remarkable routes include Silversea Expeditions, Ponant, Lindblad Expeditions, Hapag-Lloyd Cruises and Quark Expeditions.

Both journeys are scheduled for a duration in the region of 24 days, with mid to late August departures, when the ice has receded to its limits. In both cases, passengers will be required to sign a disclaimer indicating their understanding that the voyage may not be possible - ice or politics could require last minute changes!