A trip to Hawaii can be costly, but thanks to increased flight service, airfare to the islands is dropping and there's no better time to book a trip. Oahu—often called the heart of Hawaii—is a great place to start.

From palm-fringed beaches and lush pineapple groves, to staggering volcanoes and waterfalls, Oahu offers no shortage of natural beauty. And there's no better way to immerse yourself in it than by embarking on one of the island's epic hiking trails—most of which are free (or nearly free). 

Here are six hikes you won't want to miss—with views from the coast to the city and everything in between.

Diamond Head Crater

A fixture amid the Honolulu skyline, Diamond Head is an easy climb. On the ascent to the top, switchbacks afford panoramic views of the city and into the crater floor below. The final stretch—a metal staircase that winds through historic bunkers—opens to coastline views of Waikiki and the cerulean sea. You can park at the base of the crater for $5 per car, or park outside the park and pay a $1-per-person entry fee to walk to the base (cash only). The last entrance time is 4:30 p.m. and gates to the park close at 6 p.m. daily.

Makapu’u Lighthouse Trail

Don’t be fooled by the completely paved Makapu’u Lighthouse Trail—you'll work up a sweat on the incline. Just two miles roundtrip, this hike is a favorite among families with strollers or small children, as there's no need to worry about footing and there are plenty of places to stop and enjoy the ocean views. At the top, you'll see the lighthouse and on a clear day neighboring islands will come into view. Get here early to secure free parking. Beware: There's no shade along the trail, so make sure to pack sunscreen. (Tip: Be sure your sunblock is labeled "reef safe." In spring 2018, Hawaii became the first state to pass a bill banning sunscreen that contains chemicals known to damage coral reef.)

Koko Head Crater

One of the most grueling hikes on the island, Koko Head gives the StairMaster a run for its money. The trail comprises 1,048 railroad ties that scale the side of a steep crater, where an additional 20-30 feet of pathway lead to the lookout points. The best time to climb here is before or after peak sun hours. We recommend that you arrive early (parking is free at the base of the summit), and pack ample water and sunscreen. There's no shade on this hike either, and even the most fit individuals work up a good sweat. But it's worth it for the top-of-the-world views of Hanauma Bay and Hawaii Kai.

Pu’u O Hulu (Pink Pillbox Hike)

The trail entrance for Pu'u O Hulu is tucked within a neighborhood on the west side of Oahu. Follow Kaukama Road to the ninth light pole (no joke), and you can park along the curb. Once on the trail, several dusty-but-easy switchbacks lead to the top. There, you’re greeted by a bubblegum-pink pillbox with sweeping views of Waianae and Farrington Highway below.

Lanikai Pillbox Hike

Recently re-opened following a restoration of the bunkers, Lanikai Pillbox is a short, easy hike (about one hour round-trip) that offers some of the best views on the island. A short initial incline leads to flat pathways and gradual inclines before reaching the top where you can see the coastline of Kailua all the way down to Lanikai and the Mokulua Islands (the Mokes) off shore. While the views are breathtaking along the entire hike, don’t stop at the first pillbox. Keep going to the second one before turning around and heading back the same way you came up. The hike entrance is located within a neighborhood directly across from Mid-Pacific Country Club, so be respectful of residents and park down the hill along the curb.

Kaena Point

Accessible from both the west (Waianae) and north (Mokuleia) sides of the island, Kaena Point is a scenic state park and home to a sanctuary for seabirds. The most difficult part of this trail is the absence of shade; otherwise, it's mostly flat with a few slight inclines that are easy to navigate. With the ocean on one side and a mountain range on the other, there's no shortage of beautiful scenery along the 3.5-mile stretch. Be sure to pack plenty of water, sunscreen, and a snack—this hike can take up to 4 hours.