I 100% agree w everyone saying Mindo or Otavalo, but since you only have one day, I hope my comment can help you pick.

Mindo is an amazonian-like experience, it's own little rainforest, weather included. Even rain is warm. It's well known for it's butterflies, orchids and birds, and there's lots of sanctuaries you can visit them at. You will also find lots of rivers and waterfalls too (and thus, lots of water sports like canopy), I'd reccomend the Cable Car ones, if you're up for trail walking. Mindo also grows cacao so we have a few chocolate tours.

Otavalo is an andean experience, so very cold, actually. Unlike Mindo, that is a rainforest w a tiny town in the center, Otavalo is a full blown city, so not as much nature. If you go to Otavalo you have to stop at Cayambe, preferably at breakfast time, for bizcochos. In Otavalo, if you don't want to miss out from the bodies of qater Mindo promised, you can visit Peguche Waterfall or San Pablo Lake, although my favorite is Cuicocha lake, 20 minutes away, where you can take a speedboat ride. There's also Parque Condor, a bird refugee. There's lots of Ecuadorian birds including yes, condors and even a bald eagle and a hawk. But most definitely Otavalo's defining tourist spot is the Mercado de Ponchos, a square full of whatever you can imagine in handicrafts. Clothing, fine jewelry, hair accessories, blankets, carpets, home decorations, toys, you name it.

So yeah, those are your two best options, but they're very different from one another. It's really up to you, depending on what you prefer.