While it may not be the most adrenaline-pumping thing you can do in Iceland, a trip to the world renowned glacier lagoon at Jökulsárlón should certainly make its way to the top of the docket on your way around the Ring Road. This is unarguably one of Earth's great natural spectacles, with ducks and seals swimming alongside giant chunks of glacier that float in otherworldly beauty atop looking-glass water, all to the backdrop of looming ice sheets and black sand beaches. April through October, you can even hop on overpriced boats (at $32-$52 USD per adult, it pays to be the only game in town...) to get an up-close and personal view of these giants, although the experience has a "Maid of the Mist" feel to it (minus the spray).
If you've come all this way, we highly recommend taking an extra half-hour to walk the volcanic coastal beaches that stretch in either direction along the meeting point between Jökulsárlón and the North Atlantic. Not only is the experience less crowded, but there's an eerie beauty to appreciate as the remains of these beautiful icebergs resign themselves to warming waters and their inevitable fate. There's also a purported "Banksy" original (headless bear pushing a shopping cart) painted on the east pillar of the bridge, although, really, who can say for sure? Either way, it just adds to the overall magic of this place.