The Vivarium de Sa Sèquia is a small, educational natural area beside the estany Pudent, in northern Formentera, within the Parque Natural de ses Salines. It takes its name from the channel dug in the 18th century to connect the salt lagoon, the largest on the island, with the sea. This is the most biodiverse spot on Formentera and one of the finest places for birdwatching: flamingos, storks and one of Europe's largest concentrations of black-necked grebes. You reach it via the camí des Brolls, where you'll find information panels and an observation screen. It's best early in the morning, so bring binoculars.