Denver is the mile-high city, and we will be leaving it and heading into the mountains, at an even higher altitude. At this high of an altitude, the sun shines very directly and harshly - sunscreen is an absolute necessity. Additionally, it is easy to become dehydrated so you need to be careful to drink a lot of water. Some people can feel sick when adjusting to a high altitude, but most people who hydrate should feel fine. If you have more questions about this, just contact us!