The Hanover Fairground is an exhibition area in the Mittelfeld district of Hanover, Germany. Featuring 496,000 m² (5.3 million sq.ft.) of covered indoor space, 58,000 m² (624,306 sq ft) of open-air space, 27 halls and pavilions and a convention centre with 35 function rooms, it is the largest exhibition ground in the world.
The convention center was built 70 years ago after World War II and has always hosted massive trade shows, the largest being Hannover Messe, then named Exportmesse 1947 was first held in 1947 to promote the economic recovery in the Bizone.
The concept proved to be successful, and so a permanent fairground was established, growing over the years.
This industrial fair is the gathering of several tech shows in the same place at the same time. Overall, it counts more than 5,000 exhibitors and 210,000 attendees.
According to en.wikipedia