Hannover Messegelande.   

Largest exhibition center in the world. Located in Mittelfeld district of Hanover, Germany, Messegelände Hannover, or the Hanover Fairground in English, is the largest exhibition center in the world, with . 496,000 m² (5.3 million sq.ft.) of indoor space, 58,000 m² (624,306 sq ft) of open-air space, 27 halls and pavilions and a convention center with 35 function rooms. Messegelände Hannover was converted from an aircraft works and formally opened as an exhibition center in 1970.

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Shenzhen World.   

Second-largest exhibition center in the world. Inaugurated in 2019, the Shenzhen World exhibition center is the largest exhibition center in China, overtaking the Shanghai National Exhibition And Convention Center. Its indoor capacity for Phase 1 totals 410,000m², with 16 typical halls each 20,000 sqm and 3 specialty halls - 50,000 sqm (Hall 17) and 20,000 (Hall 18 and 20). When fully completed, it is expected to be the largest exhibition center in the world with an indoor capacity of 500,000m², exceeding even Hannover Messegelande (currently with an indoor capacity of 496,000m²). 

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National Exhibition And Convention Center. Third-largest exhibition center in the world. Opened in 2015, National Exhibition And Convention Center of Shanghai (NECC) is the third-largest exhibition center in the world, with an indoor capacity of 400,000m². The design of NECC is inspired from a "four-leaf clover" with a plaza at the core and four exhibition halls as its "leaves". It is located in close proximity to the Shanghai Hongqiao Airport and Hongqiao Railway Station.

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Frankfurt Main Messegelande. Second-largest exhibition center in Europe. Opened in 1909, Frankfurt Main Messegelande of Frankfurt, Germany, is the second-largest exhibition center in Europe, with an indoor capacity of 367,000m². The exhibition center is owned by Messe Frankfurt which is the world's largest trade fair, congress and event organizer with more than 2,500 employees worldwide.

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 Compare Frankfurt Main Messegelande with Fira De Barcelona Montjuic from Spain.