1Iceland
In between getting an up-close look at Iceland's renewable energy efforts, Zac soaks in a spa with Darin, samples reindeer and views natural wonders.
2France
Before heading to Paris to learn about its tap water system, Zac joins pal Anna Kendrick for a lesson in H20, courtesy of a water sommelier in LA.
3Costa Rica
Zac and Darin try out life at a swanky eco-village committed to a small environmental footprint, visit a wildlife refuge and enjoy a zip lining trip.
4Sardinia
On an island that boasts a notable number of centenarians, Zac rethinks his view on nutrition as he ponders how the locals live such long, healthy lives.
5Lima
Following a crash course in apple growing, Zac and Darin head to Peru to delve into potato cryopreservation, biopiracy and the sport of sandboarding.
6Puerto Rico
In the devastating wake of Hurricane Maria, Zac explores sustainability in the region, where he meets chef José Andrés, milks a goat and eats ceviche.
7London
After a beekeeping stop on a New York City rooftop, Zac checks out London's pollution-reduction efforts, from wall gardening to trash collecting.
8Iquitos
Zac boosts his immune system in the Amazon rainforest before climbing a tree, exploring ayahuasca tourism and watching his dinner wriggle on a plate.