A country of spectacular fairytale castles, iconic landmarks, and brilliant brutalist structures, Germany is home to its fair share of amazing architecture. But what about the properties that have become famous for very different reasons? From a cartoon-esque apartment building in Brunswick, to an upside-down home in Trassenheide, these might just be the most bonkers buildings in Germany.

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Could this be the world's tiniest castle? Burg Pfalzgrafenstein lies on a small strip of land in the middle of the Rhine River in Oberwesel. Also known as Pfalz Castle, the property is about the same width as the island it sits upon. In fact, according to My Magic Earth, it's roughly 167 feet long, 69 feet wide and 82 feet high.

Its central tower was erected by King Ludwig of Bavaria in the late 1320s and despite its miniature scale, no local would dare ignore it...

That's because the castle was constructed for one very simple reason – as a toll station. Back in the day, a large, metal chain ran from the exterior of the castle to the land on either side of the island. Any sailors passing through would have been halted by the chains and had to hand over their gold in order to continue on their way.

According to local legend, those who failed to cooperate were thrown into the castle’s dungeon. Tolls ceased to be collected in 1867 and today it's a tiny museum.

Despite its vivid pink exterior, this one-of-a-kind property is named the Grüne Zitadelle, or the Green Citadel. It's located in the central German city of Magdeburg and was opened to the public in 2005, after a two-year project.

The building isn't actually a house, though, it's a large complex of shops, eateries, and apartments. There's even a hotel and a kindergarten inside. 

The unique property was designed by Austrian architect, Friedensreich Hundertwasser, who described it as an “oasis for humanity and nature in a sea of rational houses."

It's also said to have cost about €27 million (£23m/$29m) to build, and with all of those windows, turrets, unusual embellishments, and extensive green roof, it's really no wonder.

This unusual building rises above the German city of Darmstadt like a fairytale castle emerging from a cloud forest. Waldspirale – or forest spiral in English – might look like a fantasy realm "drawn by a horde of happy children", but is in fact an apartment building also designed by Friedensreich Hundertwasser. 

Building began in 1998 and Waldspirale was completed just months after Hundertwasser's death in February 2000. 

The surreal building features a 12-storey tower, ornate golden domes and a grass roof planted with lime, beech and maple trees. Its colourful facade is said to reflect the soil layers found in the earth beneath the building, while trees – known as 'tree tenants' – grow out of some windows. 

Hundertwasser is known to have disliked order, even declaring: "The straight line leads to the downfall of humanity." Instead, he embraced non-conformity, going so far as to ensure not one of the more than 1,000 windows in the building was the same. 

Weird or wonderful? This kindergarten in Karlsruhe is definitely one for cat lovers. The quirky Kindergarten Wolfartsweier was built to resemble a big white crouching feline.

The unusual building was constructed in 2011 and designed by architects Tomi Ungerer and Ayla Suzan Yöndel.

Bound to be a hit with the kids, the building includes a door for a mouth and windows for feline eyes. The cat's tail, which is located at the back of the building, doubles as a slide. Talk about fun!

Germany is filled with amazing castles with prominent towers, but have you ever seen a half tower before? This striking property lies in Lübeck and is essentially a half-timbered house that was built into a hollow section of medieval wall, from as far back as the 13th century.

Halbturm-Haus, or Half Tower as it is often known, was constructed in 1672 by an architect who wanted to rescue the derelict fortification.

Quite aptly, the house is positioned on a street called An der Mauer, which translates to “on the wall". The historic brick tower sticks out at the back, while the white house below juts out at an odd angle, adding to the property's charms.

This might be one of Germany's weirdest homes, but there's no denying it's also one of its most attractive.

Germany is filled with mysterious architecture and oddities, and this is just one of them. The World is Upside Down in Trassenheide was completed in 2008 by Polish architects Klaudiusz Golos and Sebastian Mikiciuk.

Everything about the property has been flipped on its head, except for a set of outside steps that lead to the attic. 

The installation was designed to provide visitors with a new perspective on everyday living. Inside, the house is difficult to get your head around.

All of the furniture and fixtures are stuck to the ceiling, with everything from the sofas, to the indoor plants and toilet looking as though they’re defying gravity. Now a popular tourist attraction, the pad is an optical illusion of epic proportions.

Known as Happy Rizzi House, this colourful, cartoon-like building in the city of Brunswick is surrounded by historic homes. Described as a day-glo masterpiece, the quirky and playful property was designed by New York-based pop artist, James Rizzi, and architect Konrad Kloster. 

The striking structures are decorated in vibrant hues and hand-painted cartoon faces, giving the buildings a definite 90s TV show aesthetic. While some of the buildings are home to retail stores, others are apartments.

Unsurprisingly, Brunswick residents weren't immediately taken with the artful property, but over time Happy Rizzi House has become a much-loved piece of local architecture.

From a distance, this striking, Gothic-inspired castle in Passau, a city on the Austrian border, looks like many of the ancient palaces that can be found scattered across Germany.

Yet this property is quite unlike any you might have seen before, because it was constructed almost entirely from pieces of broken glass. 

Aptly named the Broken Glass Villa, or Glasscherbenvilla, the castle is covered in a mesmerising display of mosaics, each formed from blue and green-coloured glass, as well as bits of old ceramic crockery, and tiny Jesus statues.

It was designed by architect Aristide Ostuzzi in the early 1900s and although it fell into disrepair over time, it was lovingly restored in the early 2000s. Lucky passers-by can soak up the unique splendour of this weird and wonderful home.

Fans of UFO homes or quirky architecture will no doubt already know about Futuro houses. These funky, prefabricated properties – which resemble flying saucers – were designed by Finnish architect, Matti Suuronen, in the late 1960s.

Fewer than 100 were built around the world, making them highly rare and extremely sought-after. Yet luckily for us, there's one right in the heart of Munich that's just waiting to be explored.

The pad was constructed in 1968 and can be found next to the Pinakothek der Moderne, the city’s modern art gallery. Since there are so few Futuro houses around today, this is one of the most easily accessible examples anywhere in the world.

While the exterior can be viewed 24 hours a day, the interior is open at set times, so if you're planning a visit, be sure to check in advance. 

We know what you're thinking – there’s nothing out of the ordinary about this rather impressive property. Well, you'd be wrong! Brusttuch House in Goslar, a town in Germany’s Harz Mountains, was finished in 1521, but the architect who designed it wasn't interested in sticking to traditions.

In fact, they were very much ahead of their time. Designed with hardly any right angles, it isn't just the home's roof that is a little bit peculiar...

That's right, as soon as you get close to the trapezoid-shaped building you'll be able to spot the humorous reliefs that decorate its façade.

The cheeky carved panels depict everything from a lady riding a goat backwards, to a young maid churning butter with one hand and scratching an itch with the other. The architect definitely had fun while penning his designs...

Combining two of Germany's most iconic architectural styles, Bensberg Old Castle is part medieval fortress and part Brutalist apartment block. The property is located in the small German town of Bensberg and although it might look like two separate buildings, it's actually an important local landmark. 

The beautifully brutal building dates back to the 12th century and was originally a hilltop fortress. Over the centuries it was also used as a hospital and a monastery. 

By the 1960s, Bensberg was in need of a new town hall, so the then defunct castle was given a rather unusual makeover, thanks to expressionist German architect, Gottfried Böhm.

He restored the building's ancient towers and walls, before adding a brutalist 60s extension that sits on the old foundations of the fortress. The building later won a Pritzker Prize for Architecture, but unsurprisingly it still divides local opinion.

With a name like Castle Frankenstein, it's no wonder this ancient building has gained a reputation. Nestled in Mühltal, Hesse, the property has become synonymous with mad science experiments.

In fact, the castle's former owner, Johann Konrad Dippel, is rumoured to have inspired Mary Shelley’s 1818 novel, Frankenstein.

Dippel was born in Burg Frankenstein in 1673 and was a prominent alchemist in his later years. According to local lore, Dippel would create potions and perform gruesome experiments.

The building is now mostly in ruins, but its beautiful walls and unusual tower, with its semi-exposed interior, still remain for Halloween fans to explore.

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