The Wisconsin Center (formerly Midwest Express Center, Midwest Airlines Center, Frontier Airlines Center and Delta Center) is a convention and exhibition center located in downtown Milwaukee, Wisconsin. The center is part of a greater complex of buildings which includes the UW–Milwaukee Panther Arena and the Milwaukee Theatre, and was a replacement for the former Great Hall portion of the MECCA Complex. Up until July 1, 2013, the building was named after its sponsor Delta Air Lines when Delta purchased naming rights to the facility in August 2012. Delta later terminated its naming rights at the center on June 30, 2013 and the facility was officially renamed to "Wisconsin Center" on July 1, 2013.
The building opened in 1998 and features 188,695 square feet (17,530.3 m2) of contiguous exhibit space along with a 37,506-square-foot (3,484.4 m2) ballroom. Naming rights were sold to Midwest Airlines. Skywalks connect the convention center to the nearby Hilton and Hyatt hotels. On April 13, 2010, Republic Airways Holdings CEO Bryan Bedford announced that the name would change to Frontier Airlines Center, coinciding with the consolidation of brands between Frontier and Midwest Airlines. On August 15, 2012, Delta Air Lines purchased the building's naming rights as part of the carrier's recent expansion at nearby General Mitchell International Airport. The facility changed its name from the Frontier Airlines Center to the Delta Center after Delta purchased naming rights to the building. The change was official September 19, 2012, and signage was replaced in November.
Art was incorporated early in the design stage and is the largest design-build project in Wisconsin. The Hilton's skywalk entrance foyer floor features a green floor mosaic in the shape of Wisconsin, Michigan in gold, Minnesota, pink, Iowa red, and grey for Illinois. Region inlays represent area industries and dairy cows. A half dozen flush bronze containers contain different soil types.
Its architecture reinterprets the many historic German buildings found in downtown Milwaukee. Along with art-as-design features, the John J. Burke Family Collection is scattered throughout the interior.
On the Fourth Street side of the center is an outdoor reliquary garden titled City Yard. Created by artist Sheila Klein, it contains many iconic items from Milwaukee's DPW such as fire hydrants and the classic blue police call box. Within this area are planters containing ginkgo trees and a large monument with four limestone lion heads set in relief. These architectural elements were salvaged from the AT&T building that once stood nearby. 
Artist Vito Acconci created an indoor-outdoor sculpture titled Walkways Through the Wall. Designed to integrate private and public space, these curled terra cotta colored concrete strips flow through structural boundaries and provide seating at both ends.