In the late 19th Century, Antoni Gaudi was deeply influenced by the atmosphere of forests for the interior of his masterpiece, the Sagrada Familia cathedral in Barcelona, Spain.

A century or so later, cutting edge “biomimetic” (drawing on nature in design) architecture is even incorporating living matter into its structures. The Netherland’s Sportplaza Mercator for example, is host to lush vegetation and the species utilising this on its eye-popping façade. And in Germany, the extraordinary “algae house” harnesses microalgae as a renewable energy source by growing it in transparent surfaces.

Nature is by far the richest source of inspiration and knowledge that we have

Over the decades, the field of biomimetics has shifted from looking towards nature for overall shape. Sea creatures, crab shells and spider webs are among the species and natural artefacts architects have looked to for such inspiration, says Dr Marcos Cruz, an architect and reader at University College London’s (UCL) Bartlett School of Architecture, UK.

Now, he explains, the industry is moving towards a more “environmentally nature inspired understanding” of how nature responds to its environment and how humans can do the same.

A major driver for architects looking ever-more closely to the natural world for construction lessons is the pressing need to build with limited resources in the face of shrinking material and energy supplies.

“We have to make buildings that do more, using less… The example of where that works the best is nature itself,” says Dr Rupert Soar, a lecturer at Nottingham Trent University, UK and engineer at company 3D Blume. “Nature is always fighting to use limited resource most effectively to exist with, and we are entering that era ourselves.”

Soar himself studies termite mounds to see how we too can create cleverly designed ventilated buildings that use minimal energy, much like these extraordinary little insects have already perfected.

“We’re dedicated to trying to understanding how termites build because we believe that we can make buildings as good, as clever as termite mounds for our own buildings,” he tells BBC Earth.

For Cruz, we still have much to learn from nature: “In a way current buildings are still very crude when compared with what nature does.”

And he adds: “Nature is by far the richest source of inspiration and knowledge that we have.”

In recognition of that notion, here are nine of the most incredible and unusual nature-inspired buildings ever designed.

1. Sagrada Familia

Gaudi’s stunning buildings in Barcelona, Spain, remain a legacy to his life-long belief that we need look no further than nature to see construction at its supreme. The most ambitious of his works is the Sagrada Familia cathedral. Gaudi took over design in 1883 and the building is due to be finished in 2026, 100 years after his death (tragically, he was hit by a tram and died days later on 10 June 1926, aged 73).

The cathedral’s awesome interior is inspired by the idea of a forest that invites prayer.

Tree-like columns branch off near the roof for support, and in-between skylights contain green and gold glass to reflect light.

Enhancing the feeling of standing on a forest floor and Gaudi's plan to create a contemplative atmosphere are large coloured glass windows letting in dappled sunlight.

2. Milwaukee Art Museum

The elegant Milwaukee Art Museum’s most eye-catching feature is its huge sunscreen roof – the Burke Brise Soleil – which is reminiscent of great white wings thanks to an open and closing mechanism controlling the 90 tonne screen.

Architect Santiago Calatrava wanted to incorporate both the urban and natural features of Lake Michigan, which the building overlooks, and took into account the “culture” of the lake front including boats and sails.

Gabriel Tang, an architect and senior lecturer at Sheffield Hallam University in the UK, describes why this US building is among his favourites: “Although expensive and technically complex, this is a delightful way in which architecture can be inspired by observations and ideas from nature to create pieces which are interestingly functional, functionally practical, and practically beautiful.”

He adds: “I love the direct and straight-forward legibility of the building. The opening or closing mechanism is gracefully poetic, but yet performs a function – that of protection.”

3. Kunsthaus Graz

Like some colossal, stranded deep-sea blob, the biomorphic Kunsthaus Graz rises up amid angular, red-roofed buildings.

Dr Marcus Cruz, who was involved with planning the Kunsthaus in Austria along with main architects Peter Cook and Colin Fournier says the building took inspiration from natural forms but didn’t mimic them exactly.

Cruz’s own research included looking at microscopic images of sea creatures.

“We always imagined it as a building that was responsive," he says. "So the nozzles that exist on the roof that are very distinct – they were supposed to move and interact with the sun. And we always thought about the skin as being like a creature – creating areas of opacity and transparency and translucency, and it would vary according to these environmental changes and changes of use.”

“So the building was really seen as a sort of biotechnological creature, rather than a traditional building, an inert building.”

4. National Taichung Theater

Toyo Ito drew inspiration from the formation of rocks, caves and the transience of water for his design for The National Taichung Theater, which he hoped would provide a soft and mellow respite within the city of Taichung, Taiwan.

“Such geometries were totally unthinkable before,” says Cruz. “This could never have been done before the digital era.”

“Computational tools are currently enabling us to draw and design buildings in such a manner that then the fabrication tools in the factories and on site can replicate that on a larger scale, with a high level of precision and rigour.”

5. The Gherkin

“This was one of the first environmentally progressive buildings in the UK city of London,” says Tang of 30 St Mary Axe, the UK’s iconic skyscraper more commonly known as “The Gherkin”.

Completed in 2004, the 180m tower has an air ventilation system similar to sea sponges and anemones, Tang points out.

These creatures feed by directing sea water to flow through their bodies.

And similarly, The Gherkin is supported by an exoskeleton structure, and is designed so ventilation flows through the entire building.

6. Eden Project

The Eden Project, nestled in a clay pit near the hamlet of Bodelva in Cornwall, UK, houses an extraordinary collection of plant species from tropical rainforest and the Mediterranean.

But the domed building itself is a large part of the spectacle: its “curvilinear” shape is an example of “softer edge” geometries which fascinate architects today, says Cruz.

Architect Nicholas Grimshaw’s huge transparent semi-spherical creations were inspired by the shape of soap bubbles, and the building’s “Core” education centre mimics the Fibonacci spiral pattern found in many natural objects such as pinecones, pineapples, sunflowers and snail shells.

7. The “algae house”

Germany’s extraordinary “algae house” or BIQ building in Hamburg actually incorporates living matter – microalgae – into its design.

One side of the green-hued tower’s largely transparent surface contains tiny, growing algae which can control light entering the building and provide shade when needed.

It’s the world's first example of a “bioreactor façade”.

Algae produced within the transparent shell are continuously supplied with nutrients and carbon dioxide by a water circuit which runs through the building’s surface.

The algae creates a sun filter, explains Cruz: “In winter for instance, when there’s hardly any light and Hamburg is pretty grey for a long period, then the algae will not propagate and the façade screens will be very transparent, and so light comes through.”

When enough algae have grown they can be harvested and used to make biogas (a renewable energy source made from raw materials) to supply the building.

The ingenious design was completed as a prototype for the International Building Exhibition in Hamburg in 2013.

8. The Eastgate development

Architect Mick Pearce’s vision for the Eastgate centre in Harare, Zimbabwe, was sparked while watching termites construct their nests on the BBC television series Life.

Inspired by the way the insects use very limited resources to create ventilated mounds, permeating them with holes over the surface, Pearce set out to construct a building also peppered with holes all over the building’s “skin”, says Rupert Soar.

The result stands as a pioneering example of “passive ventilation” – the idea that buildings use renewable energy from the environment around them in place of normal air conditioning and heating systems. The Eastgate building uses less energy and is comparatively cheaper to run, according to its makers.

The tower’s “skin” takes heat from outside air during the day and absorbs it into the structure’s body. The air is cool when it reaches the middle of the building. And at night the heat that’s been absorbed during the day warms this cool air, creating comfortable cool or warm conditions for people inside.

“[Eastgate is] probably the best example of the word 'biomimicry' that’s out there at the moment,” says Soar.

9. Downland Gridshell Building

The light and airy Downland Gridshell Building, part of the Weal & Downloand Open Air Museum in Singleton, Chichester, UK was completed in 2002 and uses oak laths bent into shape to create the double-curvature, lightweight shell structure.

“This is perhaps not a building that was inspired by natural observations but with its timber cladding on the outside and being located within the woods, this building strikes a very close relationship to its natural setting and has been described by critics and architects themselves as an armadillo,” says Tang.

Tang, having worked extensively with gridshell design, explains lightweight shells such as those seen in the Downland Gridshell Building, are typically made with timber or steel. “Imagine how a bird creates a nest from separate pieces of straw. These structures usually have light-filled interiors but because of the number of connections, can be difficult to make weather-tight.”

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