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.