Question: When did the Music Concourse begin to undergo a series of improvements?
About the article "Golden Gate Park", section "Music Concourse Area".

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Major features.
Music Concourse Area.
The Music Concourse is a sunken, oval-shaped open-air plaza originally excavated for the California Midwinter International Exposition of 1894.
Its focal point is the Spreckels Temple of Music, also called the "Bandshell," where numerous music performances have been staged.
It includes a number of statues of various historic figures, four fountains, and a regular grid array of heavily pollarded trees.
Since 2003, the Music Concourse has undergone a series of improvements to include an underground 800-car parking garage and pedestrianization of the plaza itself.
It is surrounded by various cultural attractions, including:
A concourse is a place where pathways or roads meet.
Concourse may also refer to:  Concourse House, in Liverpool  Concourse Plaza Hotel, in the Bronx  Concourse Program at MIT  Concourse at Landmark Center, in Atlanta  Concourse on High, Bahá'í concept  IND Concourse Line  Music Concourse, in San Francisco  The Concourse, Chatswood  The Concourse, in Singapore  Winter Street Concourse, in Boston  
Currently improvements are being made to widen concourse C. Concourse C will be given the level of amenities found at the A and B concourses in approximately of new food and retail space.
On April 30, 2013, the airport opened the new concourse C security checkpoint, with nine security lanes, the most at the airport, as well as a new concourse A/B-C connector.
The Federal Aviation Administration is currently in the process of designing a new air traffic control tower that will replace the current tower.
The new tower is estimated to cost between $21 million and $26 million and be 228 feet tall.
There is no estimated start date.
On July 12, 2013, BWI Airport and the Maryland Aviation Administration launched a 3-year $125 million construction project.
This project will include modernizing concourse D, a new secure connection post security linking concourse D and E, and the new configuration of the concourses will allow 2 gates on concourse D to serve both domestic and international flights.
The project is scheduled to begin in late 2014 with an estimated completion date of fall 2016. 
The airport consists of a central terminal which is connected to either Concourse A or Concourse B. 
  Novelist E. L. Doctorow has featured the Grand Concourse in much of his writing.
In Jacob M. Appel's story, "The Grand Concourse" (2007), a woman who grew up in the Lewis Morris Building returns to the Morrisania neighborhood with her adult daughter to discover the boulevard is far from how she remembers it.
The Grand Concourse figures prominently in Tom Wolfe's novel "The Bonfire of the Vanities" (1987), where its evolution from "the summit of the Jewish dream" and the "new Canaan" to a rundown, unsafe thoroughfare is seen through the eyes of frustrated Assistant District Attorney Larry Kramer.
In the television series "Rhoda", Rhoda Morgenstern's parents Ida and Martin live in an apartment on the Grand Concourse.
Grand Concourse "Avenue" is referenced in Act One, scene one of Tony Kushner's , where Rabbi Isidor Chemelwitz describes it as a first generation immigrant settlement.
Ayn Rand mentions the Grand Concourse in "The Fountainhead", when Dominique decides to have a justice of the peace in Connecticut marry her to Peter Keating.
To speed the trip, Keating tells her to "get to the Grand Concourse.
Fewer lights there."