Delaware North and Boston Properties have broken ground on a $950 million expansion of TD Garden, transforming the complex into 1.87 million sf mixed-use venue called “The Hub on Causeway,” with a residential tower and office tower sitting atop a podium connecting North Station, TD Garden, and Causeway St.  Phase 1 is a $285 million glass podium named “Champion’s Row,” with a 20,000 sf sports bar and 50,000 sf entertainment venue.