The island you can drive to....

This is the Plum Island River, without which Plum Island wouldn't even be an island!   There's a two-lane road from Newburyport to the island, with a small bridge over the river.  Nice place to get off your bike and watch the outgoing tide.

Not a nice place to be in the event of an "event" at the Seabrook nuclear plant up the road, though.