This is called the Rockland Breakwater. It's a about a mile long walk along the granite block to the lighthouse one way. It took us just over an hour today to walk out, explore the lighthouse (which was open) and walk back.
It's an interesting walk because you can go at a slow pace (although people do jog along the rocks) and you have to watch your footing. It's also deceptive since it doesn't seem as long as it really is. In fact, I thought it was only half of a mile until I looked up information about it!
It had been drizzling and rainy most of the morning. When we had almost reached the coast, the sun came out. It turned out to be a perfect day to spend near the water.