Mar Chiquita is endorheic: water flows in, but none flows out. Rivers feed it - chiefly the Dulce, arriving salty from the north out of Santiago del Estero, joined from the southwest by the Suquía and the Xanaes - and then the desert sun takes over. Everything that evaporates leaves its salt behind. The lake fills the floor of a vast depression some 80 kilometers long and 45 across, yet it is barely 10 meters deep at most, so its size breathes with the rains. In wet years it swells; in dry ones it shrinks and grows saltier still, the salinity swinging from around 40 grams per liter to a brutal 250 - more than seven times the saltiness of seawater. Slowly, over geological time, it is destined to dry into a salt flat.

What the salt makes is life - strange, abundant, specialized life. The brine teems with tiny crustaceans and algae, and the birds that can stomach this water arrive in staggering numbers. Mar Chiquita hosts three flamingo species at once: the Andean, the Chilean, and the rare James's flamingo, their massed populations at times numbering in the hundreds of thousands. From the north come Wilson's phalaropes, small migratory shorebirds that cross hemispheres to winter here. At peak, the lake and its wetlands can hold a significant share of the entire planet's population of some of these species. The pink is not decoration; it is the pigment of the brine shrimp, passed up the food chain into the feathers of the birds that eat them.

For decades conservationists pushed to protect this place, and on 30 June 2022 they succeeded: the lake and its surrounding marshes were formally established as Ansenuza National Park, the largest national park in the country. Mar de Ansenuza, the older name, comes from the region's indigenous heritage. The park guards more than 19,000 square kilometers of lagoons, wetlands, and dry Espinal forest - one of the most important wetland systems in South America and a critical stopover on a flyway that links breeding and wintering grounds across two continents. It is, in effect, an international airport for birds, written into the map of Argentina.

On the shore at Miramar stands one of Argentina's most haunting ruins. The Gran Hotel Viena was built in stages and largely finished by 1945 for a German businessman, Máximo Pahlke, drawn by the supposed healing properties of the salt water. It was lavish - and short-lived. The Pahlkes sold it and left for Germany within a couple of years, and rumors of Nazi connections have clung to the place ever since, the kind of legend that grows in an empty building. Its true undoing was the lake itself. When record rains swelled Mar Chiquita beginning in 1977, the rising, salt-laden water crept into the lower floors and finally drowned the basement. Today the abandoned hotel survives as a museum and a magnet for ghost-story tourism, a monument to the fact that here, the sea always wins.

Walk out toward the water and the scale plays tricks on you. The far shore vanishes; the horizon is just a thin bright line where pale water meets pale sky. The air smells of salt and mud. Clouds of birds lift and settle in the shallows, and on a windy day the lake can throw dust storms big enough to be photographed from space. It is an austere, otherworldly place - not pretty in the postcard sense, but vast and alive in a way that stays with you.