See inside the world's Extraordinary Homes

The world is full of ultramodern homes that push architectural boundaries. Unfortunately, most of us don't get to step inside them and take a good look round. Until now. BBC2 (opens in new tab)'s The World's Most Extraordinary Homesis back and the new series brings some swoonworthy gems including a cross-shaped home offering two-way views from every room and a see-through swimming pool. The series provides around-the-world tour of the very best in architecture and design. If you haven't had a chance to tune in, here's a sneak peek of what you're missing...

WALL HOUSE

From the road, Wall House gives little away, but crossing a contemporary drawbridge, you'll find a huge, breathtaking luxury home. Whole walls of glass and wood open up, blurring the lines between interior and exterior.Thanks to a nifty counterweight system, the walls and glass panelling glides up and down with every door opening via a remote control. And not only does this modern masterpiece overlook a golf course,the windows open right onto it, meaning you can tee off from your sitting room.

But the best bit? The double-decker swimming pool, of course. Why have one pool when you can have two? This home boasts a lap pool at ground level with another 55 tonne – but seamingly weightless – second pool floating above. Look up and watch people swimming above you, or look down to anyone working out below. Genius.

CASA NA GATEIRA

And you thought an A-frame was an interesting shape for a house? Think again. This striking mansion tucked away in the hills of Penela,the rural heart of Portugal, is snake shaped.

Casa Na Gateira might look like a bog-standard farm building from the outside, but once through the front door, it reveals itself as a truly contemporary home. The architects decided not to interfere with the landscape, creating a brilliant design that hugs the ground's original slope and turns back on itself as it steps down the terraces.

DUNE HOUSE

Built within a pine forest near the Atlantic coast, thisproperty is the brainchild ofPereira Miguel Architects and is set between two sand dunes that hug the side of building. Take a stroll up one to the roof and admire the view.

The Dune House, so called because it is set in the sandy terrain of Muda, had120 tonnes of sand excavated from its foundation to create the two artificial sand dunes that partially submerge the house on both sides. When viewed from above, the building takes the shape of a cross. The house is only ever one room thick, giving each room views in both directions.

The fact that it's built entirely from concrete – walls to floors, bathrooms and even the bed frames – gives it a clean and cohesive look.

CASA GERES

It's only on entering its beautiful, landscaped gardens that you get a first glimpse of this Portuguese stunner, anchored into the hillside and bedrock. Inside, enormous windows offer views over the dramatic landscape. The main living space is one enormousroom, with double-height ceilings, and different areas zoned only by furniture.

With no walls to interrupt the flow, furniture can move around freely to create different zones and spaces – and 'rooms' can be moved easily to offer a different view each time.

There's also something about being so dwarfed that awakes the inner child in you – there are no obstacles to stop you from running, scooting or even rollerblading to get from A to B.

To break up the space, there's a wraparound mezzanine floor offering a cosier vibe. With a lower ceiling height and big beams, this all-wood space is ideal for reading nooks, snugs, TV dens or even a study. It's a welcoming contrast against the brighter, modern space downstairs.

Flex House

Shape is the USP of this property just outside Zurich, which features wide walls of glass, ribbon curves of concrete and slender steel columns. Overlooking a lake, it cocks a design snook at the chalets next door.

Villa Am See

Built for a car fanatic, an underground garage was the starting point for this property overlooking Lake Lucerne, which comprises three futuristic glass-fronted concrete boxes positioned for optimum views.

The extraordinary man-cave was carved from rock to incorporate a fitness zone, a cinema and a pool cantilevered over the hillside.

Missed an episode? Catch the re-run on Sunday at 7pm on BBC2 or watch it online here (opens in new tab). The next episode will air on Wednesday at 8pm.