At just under 20 million people in its jurisdiction, China's capital is one of the largest cities in the world and second largest in the country (behind Shanghai). A seat of cultural and political history for longer than most countries have existed, Beijing is a contrast of marked contemporary development and the preserved customs and architecture of many dynastic ages. You'll see the effects of globalization (corporate skyscrapers like the CCTV Building and the the World Trade Center Tower III, McDonald's, commercial boulevards replacing quiet hutongs) while you're here to visit the timeless treasures of a city that satisfies every vision of the ancient Orient. You have lavish Imperial gardens (the Summer Palace and Beihai Park), ancient collections of temples (the Forbidden City and Temple of Heaven), narrow alleyways reminiscent of bygone eras (hutongs), revitalized neighborhoods bursting with Chinese character (Qianmen and the 798 Art District), and a nightlife that has seen steady growth since the turn of the millennium and a hosting of the Olympic Games in 2008.
One thing you'll immediately be struck by upon entering Beijing is its vast sense of space; not upward, as with Shanghai or Hong Kong, but in land mass, making it near impossible to see the highlights on foot. This is part of why tour operations do a killing busing people between landmarks. You can choose this route or you can plan your itinerary via Embark (shameless plug!) and travel via the cheap and highly reliable subway system, taxi cabs with license plates that start with "b", or rent out a bike or car. Buses can get quite packed and have signage that may be hard to decipher if you don't communicate in Chinese, so these may have to be a last resort.
Despite the fact that no one goes to Beijing for adventure tourism, there are a few interesting excursions beyond Fifth Ring Road that will break up the most sought after landscapes of temples, palaces, and other landmarks. There are a number of mountains that can provide a day of serene hiking, but nearby Yanshan is notable for the Simatai section of the Great Wall, Black Dragon Falls, and the via ferrata route that makes the upper reaches of the mountain accessible to less experienced climbers. The Longqing Xia Scenic Area to the north is known for its cheesy dragon elevator and gorge, where the truly adventurous complement a boat ride through giant rock knuckles with ziplining and bungee jumping activities. Mangshan National Forest Park is a hiker's paradise that begins with a lounging concrete Buddha the size of a mansion just inside the gate and the Hanshiqiao Wetland Nature Reserve Park is best seen by bike or boat and provides an unforeseen sense of variety in what Beijing has to offer. Then again, much of the Great Wall, from the over-touristed Badaling to the much more isolated and authentic Mutianyu and Jinshanling is fodder for a great day trip. For more on adventures available near Beijing, check our dedicated page.
If you're thinking China for your next trip, then make sure you hit up Beijing. Not only does it have a number of attractions that are synonymous with China as a whole (Tienanmen Square, Forbidden City, etc.), but it's an unlikely adventure experience in waiting for those willing to embark. Check out our other Beijing pages for more on its impressive culture, delicious food (Peking duck!), and the surprising nightlife of districts like Wudaokou and Chaoyang.