Managua waste water to a new water treatment plant at Las Mercedes in Eastern Managua in May 2009 relieved old concerns over water pollution and native wildlife, and brought some residents closer to the old city center and the rest of the mainland. Managua is located on the southern shores of Lake Xolotlán, also known as Lake Managua. Lake Xolotlán contains the same fish species as larger Lake Cocibolca in southeastern Nicaragua, except for the freshwater sharks found exclusively in the latter. Once a Managuan scenic highlight, the lake has been polluted from the dumping of chemical and waste water since
Managua Somoza García and his family (1936–1979), the city was rebuilt and began to grow rapidly. New government buildings were erected, industry developed, and universities were established. The city's development caught the attention of Irving Fields and Albert Gamse, who composed a musical piece about the city that became popular in the 1940s through the performances of Freddy Martin, Guy Lombardo and Kay Kyser. Managua had become Central America's most developed city. Today's references differentiate the pre-1970s Managua by labeling it as "La Antigua Ciudad," which in English translates to "The Ancient City" or "The Old City". Managua's progress came to