Visiting the Great Wall of China was, without doubt, the most anticipated moment of my trip. I chose the Mutianyu section on the recommendation of several travellers, and I do not regret it.
To get there I used transport in Beijing, combining the metro and a tourist bus. The climb is demanding but there is a cable car for those who prefer it. From the top, the views justify any effort.
One important detail: if you travel to Beijing in high season, get up early. The Great Wall of China fills with people from midday and the experience changes a lot.