Online maps now let armchair travellers explore almost anywhere in the world from the comfort of their home. But, though most places on Earth are now mapped by services like Google Maps and Google Earth, there are still some mysterious spots that aren't. Here we reveal the places that don't exist on the map.

You'll find the little town of North Oaks in Minnesota pinned on Google Maps – but you can't snoop around the municipality on Street View. All Street View data was removed at the request of local residents, who begrudged images of their home town being available to strangers on the internet.

The town has some 4,500 residents and is privately owned by locals in its entirety. Claiming that Google trespassed on North Oaks' private land to obtain images, the community threatened to take their accusations further if their wishes were not adhered to. Google complied and took the photos down before things escalated.

Until recently, the Faroe Islands weren't found on Google Street View at all, due to their sheer remoteness. But one woman's plan to strap cameras onto sheep living on the archipelago, in order to capture their surrounding landscapes, inspired the tech giant to take up the job themselves. Google proceeded to send camera equipment to locals, who helped collect the images needed. Now you can see highlights such as Mulafossur waterfall (pictured) through your computer screen.

But despite this progress, there are still vast swathes of the rugged islands that lack Street View data and, when using Google Earth, parts remain blurred and pixellated. The affected area includes the westerly island of Vágar. Though it's likely due to teething problems and the islands' seclusion, others have conspired that it's down to fishing rights or the presence of an old WWII military base.

This tank manufacturer close to the Dutch town of Amersfoort was once entirely obscured in Google Earth. Today, you can easily make out its roof among the trees, but if you try to sneak a peek in Street View you'll swoop behind the woodland and stay there. Given what's being manufactured here, some may say the secrecy makes sense.

This prison in Marseille opened in 1936 and, though it's clearly marked in map view, it's entirely pixellated on Google Earth. If you try to get a glimpse on Street View, you'll be met with a mighty stone wall.

It's not uncommon for prisons to be obscured on the platform – most cite the privacy of those incarcerated and a need for confidentiality as reasons for it. But Baumettes also made the headlines when inmates posted hundreds of selfies on Facebook, some including drugs and other contraband, raising questions about the institution's security.

This research site in Alaska studies the ionosphere – a part of the Earth's upper atmosphere. When viewed on Google Earth, it appears blurred and darkened. Theories as to why the centre is concealed abound. Some are convinced it's a UFO testing site, while others believe the US government can control the weather from this base. The complex is joint funded by the University of Alaska, the Air Force and the Defense Advanced Research Projects Agency (DARPA).

Billingsgate was once a small but thriving fishing village with around 30 homes. But the island, and its important lighthouse, was battered by storms, the fiercest of which were in 1855 and 1882. Unable to live in such inhospitable conditions, and with their beloved lighthouse eroding and tattered, the last of the island's inhabitants left by 1912. Today, what's left of the island is revealed at low tide and you can take a boat out to visit it. It does not exist on Google Maps.

The owner of this unassuming house on Princeton Road in Stockton-on-Tees was bemused to find that her house was entirely obscured on Google's Street View. The occupier herself saw no reason that the property should be hidden and Google have made no comment. Some speculate that residents were simply too close to the window when Google's car came round to take photos, and the house needed to be obscured for privacy reasons. It remains a mystery. 

Keowee Dam, which created man-made reservoir Lake Keowee, was once completely blurred out on Google Earth. As well as being a source of hydroelectricity, the lake water is used to cool nuclear reactors for the adjacent Oconee Nuclear Station. Today, you can spot the dam on Google Earth, but it is not pinned, so you'll only find it if you know what you're looking for. Aside from its connection to nuclear power, the reason for the blurring remains unclear.

This site is both the official residence of the Vice President of the United States and the home of the US Naval Observatory, an astronomical complex and scientific centre. The latter has been in its current location since 1893, while the first Vice President to move into Number One Observatory Circle was Walter Mondale in the 1970s.

On Google Earth, the complex remains almost entirely obscured by trees and slightly pixellated. Theorists have mused that the haziness is to guard the Vice President's privacy, to protect confidential research carried out at the observatory, or because of an alleged secret bunker concealed below the property. Google have refuted this.

When viewed on Google Earth, the Super Brand Mall in Shanghai, and the area around it, appears confused and distorted. Faint lines labelled with road names obscure the satellite images below. The roads shown actually belong to the surrounding area, but they're several hundred metres away from where they're supposed to be. Vast swathes of the country are affected by this mapping issue.

The issue is what's known as the China "GPS shift or offset problem". It's complicated, but it's essentially a clash between the coordinate system used in China and that employed by most other countries. Most digitised maps operate on the World Geodetic System 1984, while China uses a different one: GCJ-02 datum. It's this incongruity that causes the offset.

This sizeable city in The Philippines' Bukidnon province was one entirely obscured in Google Earth. Today it remains a little pixellated with particularly patchy spots, and the detail does not improve if you zoom in.

The reason for this is unknown but, of course, there's no shortage of conspiracy theories. While some put it down to technical issues or mere oversight, others insist the city is the headquarters of the government’s missile defence programme.

This oil refinery is close to the Hungarian town of Százhalombatta, around half an hour's drive from Budapest. The site was once entirely blocked out by a large green rectangle on Google Earth – though this has now been removed, the area still appears darkened and blurry.

The obscuration has baffled users, and the usual conspiracy theories are few and far between. The most popular conclusion is that the refinery itself requested that their complex be concealed for privacy. Much like the satellite imagery, the real reason remains hazy.

This remote South Pacific atoll remains blurred and pixellated on Google Earth. Some assume this is because Moruroa was the site of controversial nuclear tests by France until the 1990s. According to some reports, the Assembly of French Polynesia had been prepared to sue France to the tune of one billion dollars for reported damage caused by the tests.

Most of us are familiar with the beaming countenance of Colonel Sanders, the founder of chicken joint KFC. But if you stumble across the fast-food outlet in Google Street View, the face of the famous chicken connoisseur may well be obscured. This is due to Google's facial recognition technology, which pixellates human faces for privacy. The same applies to various adverts around the world.

This park in the south of Chile's Chiloé Island was once completely excluded from Google Maps. Today it is marked by a pin, and you can take a look in Google Earth (though Street View remains unavailable). Some speculate that the park was concealed in order to protect its endangered species from poachers.

The Dutch royal family's three opulent residences were once entirely pixellated on Google Earth. Huis Ten Bosch and Noordeinde Palace in The Hague, and The Royal Palace in Amsterdam, were all obscured from view, most likely to protect the privacy of the royals. Today, all the palaces are clearly visible in satellite view, and you can even explore some of the lavish rooms in Street View.

A seemingly random area of the Russian tundra, not far from the city of Egvekinot, was once blurred out in Google Earth with a hazy white blob. No such marking is visible here now, but speculations are still afloat. Some conspirators call the site a "secret city": a supposed nuclear research site. Others think it was a missile zone. No such speculations have been confirmed.

This chunk of the US-Mexico border was previously obscured on Google Earth by a series of wavy, white lines. Some speculated that the blurred area was a common drug-trafficking route – this has not been verified. Now the area is perfectly crisp and you can also drop in on Street View.

Japan's Minami Torishima Airport was previously blurred in Google Earth, though it is now clearly visible. Since the airbase is operated by the country's Maritime Self-Defense Force, and was once a military airstrip, most believe the site was concealed for confidentiality.