When it opens its doors to customers on May 15, the Apple Retail Store on Boylston Street ? located in the heart of Boston?s historic Back Bay ? becomes the largest Apple Store in the US. Customers will enjoy hands-on access to the Mac, iPhone, and iPod on the first two floors, and on the third, they?ll find a Genius Bar and Boston?s first Pro Labs, offering free, in-depth training on Apple?s pro applications.