The Renaissance Center (also known as the GM Renaissance Center and nicknamed the RenCen) is a group of seven connected skyscrapers in Downtown Detroit, Michigan, United States. The Renaissance Center complex is on the Detroit International Riverfront and is owned and used by General Motors as its world headquarters. The central tower has been the tallest building in Michigan since it was erected in 1977. John Portman was the principal architect for the original design. The first phase consisted of a five-tower rosette rising from a common base. Four 39-story office towers surround the 73-story hotel rising from a square podium which includes a shopping center, restaurants, brokers, and banks. The first phase officially opened in March 1977. Portman's design brought renewed attention to city architecture, since it resulted in construction of the world's tallest hotel at the time. Two additional 21-story office towers (known as Tower 500 and Tower 600) opened in 1981. This type of complex has been termed a city within a city. In 2004, General Motors completed a US$500 million renovation of the Class-A center as its world headquarters, which it had purchased in 1996. The renovation included the addition of the five-story Wintergarden atrium, which provides access to the International Riverfront. Architects for the renovation included Skidmore, Owings & Merrill, Gensler, SmithGroup, and Ghafari Associates. Work continued in and around the complex until 2005. Renaissance Center totals making it one of the world's largest commercial complexes. In July 2015, the complex was re-branded as "The GMRENCEN." Its logo was modernized and "Reflecting a New Detroit" was introduced as the new tagline. A photo-journalistic advertising campaign launched to "shine a spotlight on the people in Detroit who make remarkable contributions" to the city. Despite the name, the hotel portion is not affiliated with the Renaissance Hotels chain, also owned by Marriott. An unrelated Renaissance Hotel does exist in the suburb of Novi however. History The idea was first conceived by Henry Ford II, the Ford Motor Company Chairman of the time. In 1970, to bring his idea to life, Ford teamed up with other business leaders to form the Detroit Renaissance. This was a private non-profit development organization which Ford headed in order to stimulate building activity and revitalize the economy of Detroit. Henry Ford II sold the concept of the RenCen to the City and community leaders. Detroit Mayor Roman Gribbs touted the project as