The longest river entirely in Serbia is Morava. Its valley is the most heavily populated area in Serbia and with very rich soil excellent for farming.Through Serbia flow many other rivers including second largest in Europe - Danube, Sava, Tamis, Tisa, Drina, West and South Morava, White Drim and Ibar. The most of mountain streams are impeccably clean. These include Drina, Uvac, Milesevka, Pek. Most of the Serbia's fish species are rare in the rest of Europe endemic or endangered. There are over thousand warm and cold mineral water springs in Serbia with more than 400 premium quality drinking water springs. Fascinating springs such as Krupaj
and Mlava in the Eastern Serbia, are visited by many tourists around the world each year.