This strange building rises up like a medieval castle from the tropical vegetation on Isla Colon, the main island of Bocas del Toro province in Panama. Around 40,000 recycled bottles made from the plastic PET went into its construction. Its aim? To raise awareness about the problem of plastic waste.

On the facade and within the building are artworks illustrating how the world's oceans are being polluted. Only a small part of the globe's more than 300 million tons of plastic produced annually is recycled, according to the Future Ocean research group. Much of it lands in the sea, with between 4.8 and 12.7 million tons ending up there in 2010.

Robert Bezeau, from Canada, actually wanted to retire when he came to Bocas del Toro nine years ago. But when he voluntarily took part in an enquiry run by the island's authorities analyzing waste production, he turned into a campaigner against plastic rubbish. "If every one of the currently 7.3 billion people on the planet only drinks one bottle, that's 2.66 trillion bottles per year," he said.

Year after year, hundreds of thousands of holidaymakers come to the archipelago, mostly from the United States and Canada. Next to bohemian bars and restaurants, the islands offer an abundance of nature, such as mangroves, warm, clean waters and beautiful beaches. But that brings with it more waste, which often ends up in the sea because of the area's inadequate rubbish disposal capacity.

Around 1.5 million plastic bottles build up each year on the small 62-square-kilometer island alone. Robert Bezeau collects them and saves them for his building projects. Only the typical drink bottles made from PET can be used - other kinds contain too much oil and would therefore be too flammable.

The plastic bottles are stacked inside cages made of reinforced steel and wire to make walls before being coated in a layer of cement. Each component can fit 300 half-liter or 120 1.5 liter PET bottles. Only particular sections, like the medieval-style triangular windows, don't follow this pattern.

This kind of construction is particularly suitable for simple bungalows, which require some 14,000 bottles. Bezeau wants to build a training center to teach people in emerging economies how to use plastic bottles as low-cost construction materials. One key advantage, he says, is that the air inside the bottles can shield against the heat.

The plastic fortress is still being built. When it's finished later this year, it's set to become a holiday resort where tourists can learn about the plastic waste problem. Founder Bezeau wants to put the income generated by the resort back into training. He's hoping that, just like in other parts of the world where waste is unavoidable, rubbish can at least be used for a meaningful purpose.