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 is the second or the third-largest cosmopolitan city inhabited by Bulgarians, after Sofia and possibly Varna. According to the 2001 census, out of a population of 338,224 inhabitants, the Bulgarians numbered 302,858 (90%). Stolipinovo in Plovdiv is the largest Roma neighbourhood in the Balkans, having a population of around 20,000 alone; further Roma ghettos are Hadji Hassan Mahala and Sheker Mahala. Therefore, the census number is a deflation of the number of Roma people, and they are most likely the second-largest group after the Bulgarians, most of all because the Muslim Roma in Plovdiv claim to be of Turkish ethnicity