On our third day in Ecuador, Cary and I ventured out on our own for a day of hiking on the Pichinchua Volcano. Although it was "just a day hike" in the "hills" surrounding Quito, we gained 2,000 ft in elevation, ending at just over 15,000 ft. (for reference, Mt. Rainier is the tallest peak in the contiguous US at just under 14,500 ft. tall)
It was a gorgeous hike with incredible views of the city and surrounding hills, but as we got close to the top, we experienced our first encounters with altitude sickness (severe dizziness, headaches, and nausea) and had to turn back just before the summit. It was certainly a learning experience for us, and gave us huge respect for mountaineers who do serious summits at higher altitudes with much heavier packs.