Atlanta's Alliance Theatre opened its doors 50 years ago when it premiered Henry Purcell's "King Arthur." The theatre is now the largest regional theater in the Southeast. It has premiered Tony-winning plays, attracted A-list actors and nurtured the dramatic passions of children and young playwrights. The Alliance is celebrating its 50th season with different productions in its newly renovated theater, including a Coca-Cola stage. Michael Parver was vice president of production at the Alliance