Sankt Peter-Ording () is a popular German seaside spa and a municipality in the district of Nordfriesland, in Schleswig-Holstein, Germany. It is the only German seaside resort that has a sulphur spring and thus terms itself "North Sea spa and sulphur spring". By overnight stays, St. Peter-Ording is the largest seaside resort and has the most overnight stays in the state of Schleswig-Holstein. Geography St. Peter-Ording is situated on the North Sea coast, on the western tip of the Eiderstedt peninsula, approx. 45 km southwest of Husum. Part of the municipality lies in the Schleswig-Holstein Wadden Sea National Park. Its characteristics include a beach that is approximately 12 kilometers long and up to one kilometre wide, the dunes, the salt meadows and the cultivated forested areas, atypical for this region. The salt meadows are of special ecological importance, since they belong to the few salt meadows that remain in their natural state. In contrast to other salt meadows along the North Sea they contain numerous ponds and puddles. The landward side is flooded with sea water only occasionally and not every year, so that amphibians such as grass frogs, moor frogs and toads (Bufo bufo) live uncharacteristically close to the seashore. Even the Natterjack Toad (Bufo calamita) is able to reproduce successfully in this environment. The normal range of the tides is up to three meters. In the intertidal mudflat walks the tidal calendar should always be consulted. That the beach is so flat and smooth has made it a popular site for sail-racing, a sport similar to wind-surfing but on wheels. There are several elevated walkways through the dunes giving access to the beach. Climate As is typical of coastal regions, St. Peter-Ording has a maritime climate with mild winters and cool summers. The local climate, especially the air on the dunes and beach, salt meadows and forest, in particular, contain high levels of aerosolized salts and iodine. In addition, the low allergen content ensures particularly clean air. The spa is used extensively for thalassotherapy i.e. the medical use of sea air and water. The municipality of Sankt Peter-Ording comprises five communities: Brösum and Norderdeich, Ording and Westmarken, Bad, Dorf and Wittendün, Süderhöft/Böhl. History St. Peter-Ording is composed of several formerly separate districts. The earliest known documentary reference to the village of St. Peter, previously known as Ulstrup, dates from 1373; the name change occurred because Ulstrup had lost