The World's Most Extraordinary Homes

Presenters Piers Taylor and Caroline Quentin travel to Portugal for the first time to find another four extraordinary homes. They are keen to visit a country that has a reputation for great design and craftsmanship but is less exhibitionist than its European neighbours. Their first house is located in the Portuguese Riviera, an upmarket area west of Lisbon. From the road Wall House gives little away, hiding behind its modern castle-like wall. But crossing a contemporary drawbridge Piers and Caroline discover a huge, breathtaking luxury home of glass, wood and concrete.

Piers Taylor and Caroline Quentin travel to Switzerland. Architecture here is influenced by the neighbouring European countries and the dramatic landscape has inspired four homes that all make the most of astonishing views. They start their journey in a tiny hamlet called Jeurs, 1,300 metres up in the Alps and in the shadow of Mont Blanc. Maison Aux Jeures is a four-bedroom house, commissioned by Olivier and Celine, a young Geneva couple who wanted a bolthole to escape their hectic work life. They asked architect Simon Chessix to design something unique and bold. He built a contemporary take on a Swiss chalet - a V-shaped house, split down the middle and separated into two 45-degree angles. The exterior walls are clad with black-stained larch and the angular roofs echo the mountain peaks.

Piers Taylor and Caroline Quentin travel to Japan, a country who combines innovation with traditional design. And with land at a premium here, small is definitely beautiful. House one is in Izura, on the coast, two hours east of Tokyo. The owner Hiroshi, a fisherman, lost everything in the earthquake of 2011. His new family home, high on a hillside, is nothing like a fisherman's hut. It is a beautiful V-shaped building entirely made of wood with a dramatic design that echos the trees around it. The house is held high in the air by three large pillars of splayed wooden struts that could flex to withstand an earthquake.

Next stop is Jikka House in Izukogen. Old friends Nobuko and Sachiko wanted to create a retirement home for themselves and a cafe for the local community. Nobuko's son, an architect, came up with five linked tepee-like structures, clad in hundreds of curved pieces of cedar. Set in woodland and full of quirky decor Caroline describes Jikka as a 'fairy-tale' home.

In Japan nine out of ten people live in the city so Piers and Caroline go to Hiroshima to see Optical Glass House. Built beside a busy main road this unusual home is a peaceful sanctuary. Inside, Architect Hiroshi Nakamura designed a giant 13-tonne wall of optical glass and behind this 'crystal curtain' a beautiful internal garden with trees stretching up to the sky. Changing light and the shadows of silent passing vehicles add to the magic of this oasis. For Piers this house is 'a shrine to beauty and silence.'

The final property, 'Glass House for a Diver' is on the coast at Etajima. Owner Mr Haragami gave his architect free-reign to design a stunning coastal house. The result - an all-glass building inspired by the chambers of an ants' nest. But the real twist is the choice of rough concrete blocks that surround this delicate home; beauty hidden within a brutal exterior. It is a challenging glamorous house with spectacular views of the sea from every angle.

Piers Taylor and Caroline Quentin travel from 'the boggy parts' of south west Britain to Florida, USA, to discover how high-end design and a celebrated architectural heritage combine to produce extraordinary homes. Canal House is for sale at nearly $30million! But does a price tag like that guarantee the very best in design?

Piers Taylor and Caroline Quentin explore bold and extraordinary homes in Spain, a country renowned for experimental and fearless architecture. They include a metal home in the foothills of the Pyrenees that is more like a piece of art, an architect's home in Madrid made of seven vast concrete and steel beams and a space-age circular building in the wilderness of Aragon.

Piers Taylor and Caroline Quentin travel to India, where traditional architecture meets cutting-edge design in stunning family homes. The first stop is the House Cast in Liquid Stone. Built in the highlands outside Mumbai, it is part brutalist fortress, part traditional Indian courtyard house and designed to be like 'chocolate sauce poured over vanilla ice cream'. Nature has been fused into the design, from the basalt quarried from beneath the building to the wild grasses and trees that grow freely amongst the living rooms and courtyards - in a house where you are never entirely inside or outside.

In the epic, mountainous scenery of the Western Ghats, they discover the 'House of Three Streams.' Built by using bridges to link the only areas of the hillside flat enough for construction, it is a delicate weekend home that rests gently on the landscape. The name describes waterways that form during the monsoon rains and cascade through the building itself. With a swooping zinc roof, little in the way of walls and no front door, Piers says 'houses are better when they don't try to look like houses'.

The third home is a stunning riverside bolthole. 'Riparian' draws on Indian architectural heritage in an homage to the tea plantation Veranda house- but this one is half buried in the riverbank. The subterranean build and turf roof defend the house against the monsoon rains and scorching summer heat. But despite Caroline 'embracing her inner badger', it turns out the house is a light and airy gateway into a rural idyll.

The final destination is 'Collage House.' Piers and Caroline are greeted by a facade made up entirely of recycled doors and windows, hung within a concrete frame- all reclaimed from buildings that were demolished to make way for city skyscrapers. Inside they find a kaleidoscope of old materials, given new purpose in a witty and visually stunning family home. Leading Piers to proclaim 'the future of architecture? I think it's this'.

Piers Taylor and Caroline Quentin head to Norway, where architecture is influenced by incredible landscapes and extreme climate.

They begin on Vega Island, 600 km north of Oslo near the Arctic Circle. It is the stunning location of Vega Cottage, a truly remote family retreat delicately perched on rocks and overlooking the beach. The architects' challenge was to create a home that emulated the traditional fishermen's huts nearby and left the surrounding landscape completely untouched. The result is a beautiful but modest home - the epitome of Norwegian understatement. The second home on their journey is in Valldal, where Summer House teeters on a cliff, overlooking the beautiful fjords. Here, Jan Jensen, one of Norway's most exciting architects, has created an eye-opening eagle's nest of a home. It is a mixture of spaces built into and around the rock face with a series of elevated bedroom pods held aloft on stilts. There is also a mammoth rock face in the living room and an infinity pool hanging in space.

Piers Taylor and Caroline Quentin are in Israel where exciting modern houses are inspired by rich cultural and historical traditions. J-House house is in Herzliya, a millionaire's playground by the Med. It is a palatial white home tucked away in a suburban plot and reached by a bridge over lush gardens. Piers and Caroline discover luxurious, warm and vibrant interiors that contrast with the modernist facade. Glass walls open up to connect the entire living area with the gardens and pool.