Bad Pyrmont is a city in the district of Hamelin-Pyrmont, in Lower Saxony (Niedersachsen), Germany, with a population of 22,000 (2003). It is located on the River Emmer, about 10 km west of the Weser, and a popular spa resort that gained its reputation as a fashionable place for princely vacations in the 17th and 18th centuries. Its large park is among the most spectacular in Germany, with a renowned outdoor palm garden. The baroque castle (1706-1710), part of an impressive complex of fortifications from the 16th century, today houses the museum. Unique in Europe is the vapor cave, where therapeutic carbon dioxide vapors emerge from the earth. The town is also the center of the Religious Society of Friends (Quakers) in Germany. Bad Pyrmonter mineralwasser, popular throughout northern Germany, is bottled in Bad Pyrmont.