My husband and I visited la Reserva de la Biosfera Ria Celestun when we were in Merida for a few days over the Thanksgiving holiday. The reserve is a protected natural area that is home to nearly 560 species of animals, of which approximately 300 are birds (a third of the total bird species in Mexico)! It's not a river (but a tributary), which is why it's called Ria Celestun! We arranged for a tour from Merida (they picked us up at our hotel and drove us to Celestun), but you can also drive here yourself and arrange for a tour with one of the guides there. The guides at the Reserve take you out on a boat to look for the wildlife that call the reserve home. The main attraction is the flamingos - of which you can see a lot if you're there at the right time/season - but there is a lot of wildlife to see! We saw crocodiles, boa constrictors, spoonbills, egrets, herons, and more! The water itself is an attraction - in certain seasons, it's a clear blue, and in others, it can be pink or red (the high salt content in the water creates an environment ideal for certain algae and microorganisms that produce pink pigments). Then there's the mangrove trees, too! Mangroves are amazing - they grow in equatorial climates, typically along coastlines and tidal rivers. They have particular adaptations to take in extra oxygen and remove salt, allowing them to tolerate conditions that kill most plants! We only saw one flamingo (they're off in other waters now), but we saw lots of wildlife and got some great pictures. It was also just a great change of pace to head out to Celestun for the day (after being in Merida for a few days)! I highly recommend it as a day trip from Merida! read more