11_diagonal_street | completiondate | 1983 <tsp> 11_diagonal_street | floorcount | 20 <tsp> 11_diagonal_street | owner | redefine_properties_limited <tsp> 11_diagonal_street | architect | helmut_jahn <sep> 11 diagonal street is an office tower in johannesburg, south africa it was built in 1983 to a height of 80 metres it is designed to look like a diamond as it reflects different views of the central business district from each angle of the buildingthe building's architect was helmut jahn 
11 diagonal street is a 20 floor helmut jahn building. completed in 1983 and owned by redefine properties ltd.the building's architect was helmut jahn