Anything that puts you in regular contact with nature has a decidedly positive impact on the nervous system.
Fractals are patterns in nature that repeat at different scales. These patterns are made up of similar copies of themselves and can be found in trees, plants, seashells, crystals and snowflakes. Studies have shown that the act of observing fractal patterns generates a distinct EEG pattern in people that includes increased production of alpha waves in the frontal lobe and beta waves in the parietal lobes and has a measurable calming impact on our physiology.
Another bonus: spending at least 120 minutes a week in nature is associated with good health and well being. A recent study reported that people who spent at least two hours a week in nature or a green urban space reported consistently higher levels of health and well being that those who spent less or no time in nature.