At least five major developments are planned or proposed for above and around the Massachusetts Turnpike, a level of construction around the artery not seen since the Big Dig more than 10 years ago, if not the High Spine's birth in the 1960s.

These projects include the long-stalled Fenway Center, which might finally start construction early next year, and the Viola, an S-shaped development that also involves a new Hynes Green Line station. There are also plans afoot to fill in the last two of Back Bay's so-called dead zones around the Pike.

The construction would add at least 723 apartments and condos total, if not significantly more, as well as features such as a hotel and retail space.