Gigantic factories have always been symbols of prosperity — but also of dystopian horror. Some of the biggest factories in our world today evoke ambivalent feelings of dread and awe.

Foxconn City (or iPod City), the largest factory complex of the electronics contract manufacturing company Foxconn at the Longhua Science & Technology Park in Longhua, Shenzhen, China. More than a quarter of a million employees are working there day by day, most of them for six days a week.

Journey Inside the Cavernous Interiors of these Mega-Factories

The 1.16 sq mi (3 sq km) area includes 15 factories, a swimming pool, a city centre with a hospital, bookstore, bank, grocery store and some restaurants. About a quarter of the employees live in dormitories.

Journey Inside the Cavernous Interiors of these Mega-Factories

Journey Inside the Cavernous Interiors of these Mega-Factories

Journey Inside the Cavernous Interiors of these Mega-Factories

(Photo by Daniel Berehulak/Getty Images and Wired)

The Meyer Werft Dockhalle 2, the largest roofed dry dock in the world, Papenburg, Germany

Journey Inside the Cavernous Interiors of these Mega-Factories

It was inaugurated in 2000 and later extended to a full length of 1654 ft (504 m), a width of 410 ft (125 m) and a height of 246 ft (75 m).

Journey Inside the Cavernous Interiors of these Mega-Factories

Journey Inside the Cavernous Interiors of these Mega-Factories

(Photos by Markus Hibbeler/AP, Joerg Sarbach/AP and David Hecker/dapd)

The Tesla Factory (the former New United Motor Manufacturing Inc. site of General Motors and Toyota) in Fremont, California, founded in 2010.

It's a 370-acre (150 ha) site, but only a small part of it is in use. Most of the work are done in the 5.5 million sq ft (510,000 sqm) main building.

Journey Inside the Cavernous Interiors of these Mega-Factories

(via Niall Kennedy and Steve Jurvetson)

Boeing Everett Factory in Everett, Washington, an assembly site for large Boeing aircraft. It was originally built for construction of the 747 in the late 1960s.

Journey Inside the Cavernous Interiors of these Mega-Factories

It's the largest building in the world by volume at 472.37 million cu ft (13.385 million m3).

Journey Inside the Cavernous Interiors of these Mega-Factories

Journey Inside the Cavernous Interiors of these Mega-Factories

Journey Inside the Cavernous Interiors of these Mega-Factories

(via Wikimedia Commons and Stephen Brashear/Getty Images)

The Belvidere Assembly Plant, a Chrysler factory in Belvidere, Illinois, opened in 1965. Now it makes two Jeep models (Compass and Patriot) and the Dodge Dart.

Journey Inside the Cavernous Interiors of these Mega-Factories

The factory has 3.3 million square feet (310,000 m2) of floor space on 280 acres (1.1 km2).

Journey Inside the Cavernous Interiors of these Mega-Factories

(via Chrysler Group and Autoevolution)

The world's largest single hall without supporting pillars inside: a former airship hangar in Krausnick, Germany, built in 1992. The company went bankrupt in 2002, and the hangar was sold to a Malaysian company.

Journey Inside the Cavernous Interiors of these Mega-Factories

The 1180 ft (360 m) long, 690 ft (210 m) wide and 351 ft (107 m) high hall is now called Tropical Islands Resort, a sauna and spa facility with traditional Thai buildings, a rainforest and a sandy beach, among others.

Journey Inside the Cavernous Interiors of these Mega-Factories

Journey Inside the Cavernous Interiors of these Mega-Factories

Journey Inside the Cavernous Interiors of these Mega-Factories

Journey Inside the Cavernous Interiors of these Mega-Factories

Journey Inside the Cavernous Interiors of these Mega-Factories

(via Wikimedia Commons and Tropical Islands)

The Jean-Luc Lagardère Plant, the assembly line of Airbus A380s in Toulouse, France. It has a footprint of 1.32 million sq ft (122,500 sqm)

Journey Inside the Cavernous Interiors of these Mega-FactoriesJourney Inside the Cavernous Interiors of these Mega-Factories(Photo by Pascal Parrot/Getty Images and Maarten Visser)

NASA Vehicle Assembly Building (VAB) at Launch Complex 39, Kennedy Space Center, Florida. It was completed in 1966 and was used to assemble the early manned launch vehicles and the Space Shuttles between 1968 and 2011.

Journey Inside the Cavernous Interiors of these Mega-Factories

It has the four largest doors (456 ft or 139 m high ones) in the world and the VAB is the largest single-story building (526 ft or 160.3 m) ever built.

Journey Inside the Cavernous Interiors of these Mega-Factories

Journey Inside the Cavernous Interiors of these Mega-Factories(via Wikimedia Commons, Bill Ingalls/NASA and Roberto Gonzalez/Getty Images)

Bonus: The largest abandoned factory: the former Packard Factory, a 3.5 million square-foot complex on a 35 acre site in Detroit, Michigan

Journey Inside the Cavernous Interiors of these Mega-Factories

These 47 buildings (the first industrial use of reinforced concrete) were designed by Albert Kahn in 1903.

Journey Inside the Cavernous Interiors of these Mega-Factories

More than 40,000 workers spent their workdays here until the late 1950s, when the company went bankrupt.

Journey Inside the Cavernous Interiors of these Mega-Factories

Journey Inside the Cavernous Interiors of these Mega-Factories

Journey Inside the Cavernous Interiors of these Mega-Factories

(via Joy VanBuhler, Carlos Osorio/AP and Joshua Lott/Getty Images)