are mainly located in Northern Slovakia. Driny is the only cave located in Western Slovakia that is open to the public. Dobšiná Ice Cave, Demänovská Ice Cave, Demänovská Cave of Liberty, Belianska Cave, or Domica Cave are among the most popular tourist stops. Ochtinská Aragonite Cave, located in Central Slovakia, is one of only three aragonite caves in the world. There are thousands of caves located in Slovakia, thirteen of which are open to the public. Slovakia is also known for its numerous spas. Piešťany is the biggest and busiest spa town in the country, attracting many visitors from the Gulf countries, mostly the United Arab Emirates, Qatar, Kuwait, and Bahrain. Bardejov, Trenčianske Teplice, Turčianske Teplice, and Rajecké Teplice are other major spa towns. Some well-known minor spa towns and villages are Štós, Číž, Dudince, Kováčová, Nimnica, Smrdáky, Lúčky, and Vyšné Ružbachy, among others. Typical souvenirs from Slovakia are dolls dressed in folk costumes, ceramic objects, crystal glass, carved wooden figures, črpáks (wooden pitchers), fujaras (a folk instrument on the UNESCO list) and valaškas (a decorated folk hatchet) and above all products made from corn husks and wire, notably human figures. Souvenirs can be bought in the shops run by the state organisation ÚĽUV (Ústredie ľudovej umeleckej výroby—Centre of Folk Art Production). Dielo shop chain sells works of Slovak artists and craftsmen. These shops are mostly found in towns and cities. Prices of imported products are generally the same as in the neighbouring countries, whereas prices of local products and services, especially food, are usually lower. Science The Slovak Academy of Sciences has been the most important scientific and research institution in the country since 1953. Slovaks have made notable scientific and technical contributions during history. Slovakia is currently in the negotiation process of becoming a member of the European Space Agency. Observer status was granted in 2010, when Slovakia signed the General Agreement on Cooperation in which information about ongoing education programmes was shared and Slovakia was invited to various negotiations of the ESA. In 2015, Slovakia signed the European Cooperating State Agreement based on which Slovakia committed to the finance entrance programme named PECS (Plan for the European Cooperating States) which serves as preparation for full membership. Slovak research and development organisations can apply for funding of projects regarding space technologies advancement. Full membership of Slovakia in the ESA is expected in 2020 after signing the ESA Convention.