Final answer:
The highest capital city on the eastern slope of Pichincha Volcano is Quito, with an elevation of about 9,200 feet, and is the second-highest capital city after La Paz in Bolivia.
Step-by-step explanation:
The highest capital city in the world lying on the eastern slope of Pichincha Volcano, in the Guayallabamba River Basin, is Quito. Quito is situated at an elevation of about 9,200 feet and is considered the second-highest-elevation capital city after La Paz in Bolivia. While La Paz reaches heights that exceed Quito, it is Quito that has the distinction of being next to the active stratovolcano, Pichincha, which rises to an altitude of approximately 15,413 feet above sea level and is located in the Andes mountains. In the broader regional context, the Latin American Andes range is also home to Potosí in Bolivia, one of the earth's highest-elevation cities at 13,420 feet above sea level and significant for its historical silver mining operations since the Spanish colonial era.