Plovdiv 40,000 objects. The Museum of Natural Science was inaugurated in 1955 in the old edifice of the Plovdiv Municipality built in 1880. It is among the most important museums in the country with rich collections in its Paleontology, Mineralogy, and Botanic sections. There are several rooms for wildlife and it contains Bulgaria's largest freshwater aquarium with 40 fish species. It has a collection of minerals from the Rhodope mountains. The Museum of Aviation was established on 21 September 1991 on the territory of the Krumovo airbase to the southeast of the city. The museum possesses 59 aircraft and indoor and
Plovdiv was inaugurated in the city. In the beginning of the 20th century, Plovdiv grew as a significant industrial and commercial center with well-developed light and food industry. In 1927 the electrification of Plovdiv has started. German, French, and Belgian capital was invested in the city in development of modern trade, banking, and industry. In 1939 there were 16,000 craftsmen and 17,000 workers in manufacturing factories, mainly for food and tobacco processing. During the Second World War, the tobacco industry expanded as well as the export of fruit and vegetables. In 1943, 1,500 Jews were saved from deportation in concentration camps