The north end of Kauai, has some of the most spectacular coastline and pristine beaches in all of Hawaii. In one day you can visit a lighthouse, discover a secret beach, watch surfers, explore a cave, and witness a spectacular sunset. It seems every pullout along Highway 56 has something to see.
If heading north from Kapaa your first stop should be the Kilauea Lighthouse, which is at the northernmost point of the Hawaiian islands. The lighthouse sits on a 568-foot bluff which is part of a National Wildlife Refuge. Visitor hours are normally 10 am to 4 pm. If you don't get there during business hours, it is still possible to see Kilauea Lighthouse from an overlook by the parking area.
Just west of the lighthouse is Secret Beach. To get there, take the first main road off the Highway (Kalihiwai) after the Kilauea Lighthouse then take the first right on the dirt road until it dead ends to a parking lot by some homes. There is a somewhat steep trail down to the beach. Secret Beach really isn't that secret anymore. It's just a a little difficult to find. But it is worth the effort as it is the largest beach on the north end, is not too crowded and has a nice view of the lighthouse in the distance. Swimming here is not recommended during the winter months as the surf is too rough.
If you plan on spending time at a beach, you may want to go to Ke'e Beach, which is at the furthest point traveling west on the northern part of Kauai. There are bathrooms here and the water is more calm due to a large reef. But it gets very busy here as the day progresses, so you may want to put your umbrella up further away from the parking area. It is at Ke'e Beach where one can witness the most amazing sunsets, or if you're lucky see a Hawaiian monk seal sunning itself on the beach. Also near the Ke'e Beach parking lot are a couple of wet caves worth checking out.
The end of the road here marks the spot of the famous Kalalau Trail. This is an extremely challenging hike over 11 muddy miles of steep hills and switchbacks. You can hike the first two miles without a permit. Those with permits can venture further and camp overnight. This trail is very busy and you really don't really have great views of the coastline because you are on it. If you are looking for great view of that, you would want to take a catamaran trip or helicopter tour. When hiking the NaPali Coast, I prefer the trails accessed from the top - namely the Awaawapuhi and Nualolo trails. In my opinion the views from there are better, and the trails are not as narrow and muddy. But to get there you must drive about two hours around the other end of the island to Koke'e Lodge and Museum where the trailhead is.
A great hike on the north end with a view of the surrounding mountains and Hanalei is the Okolehau Trail. Okolehau Trail is accessed by heading two miles east of Hanalei, then turning right on the road just to the west side of the big bridge. About a half-mile down the road you will see a parking lot and the trailhead. It's about a two mile hike up to great panoramic views of the town of Hanalei and much of the north end of Kauai. After hiking you'll be close enough to Hanalei or Princeville where it will be easy to find a restaurant to satisfy your hunger.