If you just have one day in Cape Cod, drive all the way up and around the Cape to Provincetown. P-town center is hilly and quaint with tiny streets, lots of bikers and rainbow flags adorning every establishment.
Near P-town center, go to Herring Cove Beach, grab a lobster roll or fried fish sandwich (this was really delicious!) at Far Land on the Sea before heading onto the sand. Shielded by the cape, there are no waves here and no sounds of the ocean, if that's your thing. But it was easily one of the best beaches I've been to.
The water was crystal clear.
FYI, seals (seen) and sharks (none seen) also enjoy the beach.
Now, snake your way down the coast. Drive all the way up to the end of a short road that leads to Highland Lighthouse, close to the town of Truro. A picture perfect lighthouse, if there ever was one, awaits you on the edge of a cliff on the Cape Cod National Seashore.
One more town over is Wellfleet. Stop by the Wellfleet Harbor and maybe grab some of their renowned oysters. We enjoyed the sunset here while watching the boats and the hang-gliders.
Heading further down through the cape, through the town of Eastham, drive up to the Nauset Lighthouse. You can walk down to the beach as well (more sharks and seals here).
End your day in Orleans, a town located where the cape turns back inward toward the continent. When we arrived, all the restaurants had already shuttered for the July 4th holiday but we found no less than 4 ice cream parlors within a mile's stretch, and all of them were packed.
Grab the Lavender Honey at the Local Scoop, with a homemade waffle cone. It's brittle and breaks apart and leaves you with a ice cream sandwich but is oh-so-good.
Oh, and don't forget to listen to Vampire Weekend while you're in Cape Cod.