Doctor Who is one of the longest-running and most loved TV shows of all time. Since 1963, the Time Lord has enthralled millions with his/her time-traveling adventures, terrifying aliens, and heartbreaking regenerations. That being said, despite the time-traveling aspect of the show, we ought to that the TARDIS is capable of traveling in space as well as time, and some of the most memorable adventures of the Doctor have come, not from time travel, but from simply discovering alien planets.

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This article will list 5 of the best worlds the Doctor has visited and 5 of the worst (discounting Gallifrey, as it's the Doctor's homeworld so it hardly counts as a visit).

Best: Pete's World

While a parallel Earth (known as Pete's World)  may not seem to be too alien a world, it was incredibly different from Earth as we know it. Firstly, Cybus Industries are incredibly influential in this world, with the technology company successfully managing to convince almost all the population (of the UK at least) to wear their Cybus Earpods, eventually leading to the creation of the Cybermen.

However, while the Cybermen are an obvious difference from our Earth and the parallel Earth, there are other more subtle differences, with the most notable of which being the blimps floating around London.

Worst: Mars

While it may seem unfair to include the home of the Ice Warriors on this list, the Red Planet is hardly one of the most imaginative planets that we've seen to appear on the BBC's favorite science fiction show. Despite the fact that some of the stories involving Mars are fantastic, there is very little about the planet that is captivating.

Aside from the characters that the Doctor encounters on Mars, there is very little about the planet that is memorable or iconic aside from the endless red desert.

Best: Krop Tor

While Krop Tor may have only appeared in one Doctor Who story, it was certainly a memorable story that was filled to the brim with mythological and mind-bending backstory.

We see that the planet is orbiting a black hole that is said to drive people mad if they stare into it for too long. However, this is not the strangest element of the planet. Beneath the planet is the Beast, a creature that claims to be Satan himself.

Worst: San Helios

In the same vein as Mars, although without the memorable and iconic stories, San Helios is a planet that was destroyed by a swarm of creatures and rendered a desert planet.

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As in the case of Mars, the planet is incredibly forgettable and has very little of interest within it besides for the iconic red London bus that the Doctor and Co traveled to the planet on.

Best: New Earth

New Earth is a planet that was made to look like the Earth of old by nostalgic humans in the long distant future. The city we saw the most of on New Earth was New New York, a swamping metropolis with dark secrets.

We first see the city in the episode New Earth, in which the Doctor and Rose visit a hospital that experiments on cloned humans. In the following season, we visit the gridlocked undercity as the Doctor attempts to free the inhabitants from the motorway.

Worst: Malcassairo

This is another entry on the list that appeared in a fantastic episode, yet did not have any particularly memorable visuals or iconic landmarks.

The planet exists at the end of the universe and is the home of the last humans as they struggle to find their way to Utopia. However, the planet itself isn’t very interesting and just appears to be another planet closely resembling a quarry in Wales.

Best: Akhaten

While Akhaten only appeared in one episode in season 7, it was certainly a memorable and interesting planet. Unlike some other alien planets in Doctor Who that consistently seem to look like Welsh quarries, Akhaten was sprawling with life and full of interesting trinkets and alien culture.

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In addition to the market place and its culture, the fact that the planet also revolved around a sentient sun also makes for an interesting addition to the mythology surrounding the world.

Worst: Orphan 55

Doctor Who Orphan 55

While some might claim that, technically, this planet is Earth, it is an entirely different world to the Earth as it currently exists. Orphan 55 is a dead planet that the Doctor visits during season 12 of the show, with the Time Lord having to escape from the future humans that have been mutated from the devastation carried out on the planet.

The reason why this world is in the 'worst' category is that the showrunners missed a huge trick with the planet. Rather than leaning into the 'devastated Earth' imagery in a Planet of the Apes-esque manner, they opted to have a baron, dusty planet on the surface. The reveal that this was Earth only came from a Russian sign underneath the planet.

Best: The Library

For book-lovers, there can be no better planet in the Doctor Who universe than the sprawling library planet that appeared in the season 4 story, Silence in the Library/ Forest of the Dead. While the planet is, clearly, not an organic creation it is still one of the most interesting planets that the Doctor has ever visited.

The entire planet is a giant library, with the planet holding every book that has ever been written. In addition, aside from the vashta narada, the library is incredibly beautiful and a truly original concept.

Worst: Ranskor Av Kolos

This planet appeared in season 11 of Doctor Whothough one could easily be forgiven for forgetting that the planet even existed. Like many planets in Doctor Who, it was a dusty, baron planet that seemed to be completely devoid of life except for the main characters and the particular villain of the week. It is this lack of imagination that sees it earn a place on this list.

It is this lack of imagination that is often the cause of planets to appear in the 'worst' category on this list. Perhaps it is due to budget restraints, but it is abundantly clear that the same Welsh quarry is reused every season in Doctor Who.

NEXT: Doctor Who: The 5 Best & 5 Worst Aliens That The Doctor Ever Met