Boston's Rose Kennedy Greenway is a swath of green right through the northern and eastern part of the historic center, from North Station to South Station.

For most of Boston's 20th-century history, this was the Central Artery, a six-lane elevated highway that provided vehicular access to the city center and connected highways leading to the North Shore and South Shore of Massachusetts Bay.

From the 1990s to the 2000s, the Big Dig, as it was called, sunk the highway (now Interstate 93) underground, leaving the highway's former track to be a park.

Forecast to cost about $3 billion, the final bill came in around $18 billion, something of a record, it seems.

The Greenway now allows pedestrians to cross from the historic center to the North End and the Waterfront through a park rather than across busy streets beneath a roaring highway.

For kids, the favorite part of the Greenway is the flat fountain that doesn't look like a fountain...but every few seconds jets of water shoot from myriad holes in the flat stone surface, seemingly at random. Kids go wild...and wet!