The most populated island. On Oahu you will find the city of Honolulu, Waikiki Beach, Pearl Harbor, and the famous North Shore known for its big wave surfing. While the island is the most populated, most of the people are concentrated in the city of Honolulu on the south shore. But on this island, you'll find rainforests, deep canyons, valleys and waterfalls, a nearly mile-high mountain range, coral reefs, and gold-sand beaches. The city proper of Honolulu -- where most of Oahu's residents live -- is approximately 12 miles wide and 26 miles long, running east to west, roughly between Diamond Head and Pearl Harbor. Within the city are seven hills laced by seven streams that run to Mamala Bay. 
Waikiki is the main hotel zone on the island. Almost all hotels on Oahu are in Waikiki. There are 4 (mostly luxury) hotels that are outside of Waikiki. These are the Marriott Ihilani, Kahala Mandarin, Turtle Bay Resort, and the New Otani Hotel.
Surrounding the central area is a plethora of neighborhoods, ranging from the quiet suburbs of Hawaii Kai to kamaaina (old-timer) neighborhoods like Manoa. These areas are generally quieter and more residential than Waikiki, but they're still within minutes of beaches, shopping, and all the activities Oahu has to offer.
The windward side is the opposite side of the island from Waikiki. On this coast, trade winds blow cooling breezes over gorgeous beaches; rainsqualls inspire lush, tropical vegetation; and miles of subdivisions dot the landscape. Bed-and-breakfasts, ranging from oceanfront estates to tiny cottages on quiet residential streets, are everywhere. Vacations here are spent enjoying ocean activities and exploring the surrounding areas. Waikiki is just a quick 15-minute drive away.
The North Shore is the Hawaii of Hollywood -- giant waves, surfers galore, tropical jungles, waterfalls, and mysterious Hawaiian temples. If you're looking for a quieter vacation, closer to nature, and filled with swimming, snorkeling, diving, surfing, or just plain hanging out on some of the world's most beautiful beaches, the North Shore is your place. The artsy little beach town of Haleiwa and the surrounding shoreline seem a world away from Waikiki. The North Shore boasts good restaurants, shopping, and cultural activities -- but here they come with the quiet of country living. Bed-and-breakfasts are the most common accommodations, but there's one first-class hotel and some vacation rentals as well. Be forewarned: It's a long trip -- nearly an hour's drive -- to Honolulu and Waikiki, and it's about twice as rainy on the North Shore as in Honolulu.
Oahu is the 3rd largest island at 604 square miles. Waikiki is only 2 square miles of the island. Many people assume that they do not need a car in Oahu. This is generally a major misconception. If you are content to only see Waikiki and not the other 98% of the island, then no car may be an option. The bus system on Oahu is OK, but do you want to waste your valuable vacation time sitting on a bus for hours at a time? Also keep in mind that a taxi is approximately $30 each way to/from Waikiki and the airport.
