A whiff of chlorine is virtually synonymous with taking a dip in a swimming pool. While it helps to kill off bacteria, it also serves as a subtle reminder that you are wading around in chemically treated water (if tasting the odd mouthful just isn't enough). Switzerland's Naturbad Riehen swimming pool is entirely chemical-free, relying instead on a biological filter system to provide clean and natural water for thousands of patrons, no itchy red eyes in sight.

A town of around 20,000 people, Riehen sits just outside of Basel on the Swiss-German border. This section of the border wraps around Riehen in such a way that in 2006, the town's old swimming pool had to be demolished to make way for a tunnel connecting two German cities on either side. With the controversial roadway completed in 2013, the people of Riehen were quick to reclaim their territory.

"The citizens wanted their pool back and believed that a natural swimming pool would suit their interest in bathing, swimming and playing, just as well as a traditional pool," Christian Lupp, Recreation and Sports representative from the Municipality of Riehen tells Gizmag. "Furthermore, there was the understanding that the natural water is better for the skin and eyes and feels smoother and softer".

The first man-made natural swimming pools date back to the early 1980s in Austria, though these were largely for private use. The precise mechanics vary between each natural pool, but they typically contain the swimming water inside a membrane and then a separate water regeneration zone to clean it. Aquatic plants kill off germs while absorbing nutrients from the water for growth. Often the water is pumped across the surface of rocks or gravel to which the bacteria clings, functioning as a natural filter.

Since the 1980s, the concept has been commercialized and spread to different parts the world. Natural pools for public use have popped up in Germany, the UK and one is currently under construction at Webber Park in Minneapolis, set to be the first in the United States. Lupp says a point of difference for the Naturbad Riehen is that it's au naturel from the ground up, allowing for better integration of the pool's natural technology with its wooden infrastructure.

"Many other projects are conversions of traditional pools," he explains. "Our pool is absolutely built from zero, allowing the extraordinary possibility of a holistic design and a combination between the natural technology and its according architecture."

Swiss architects Herzog & de Meuron designed Riehen's new swimming pool to accommodate the town's families and blend in with the greenery that surrounds. Features include a wading pool for toddlers, a separate pool with a sloping gravel beach, a water-slide, a 25-meter (82 ft) lap pool and a diving board. An on-site cafe offers refreshments and snacks, with wooden decking and grass providing a place for some time out.

Officially opening for business in mid-June, the Naturbad Riehen is equipped to deal with 2,000 daily visitors. We're guessing the residents of Riehen are pretty happy with their new pool, with the possible exception of those in the business of selling swimming goggles.

Source: Naturbad Riehen