El Altar — Sublime Mountain in English — is an extinct volcano on the western side of Sangay National Park. This is 106 mi (170 km) south of Quito, near Riobamba. Legend has it that after a giant eruption more than 500 years ago, the volcano summit completely collapsed, forming nine peaks surrounding a beautiful glacial crater lake, known as "Yellow lagoon" or "Laguna Amarilla" in Spanish. Surrounding the crater, there are green valleys full of waterfalls and multi-colored glacial lagoons. The Altar peaks resemble the shape of an altar of a colonial church. Hence, its name.
The highest point is located at about 17,451 ft. (5,319 m.), about 4–7 hours hiking, there is a refuge belonging to a Hacienda, it has basic beds, a kitchen, and hot water. From the refuge, it's another two hours across the valley and up to a steep hill to the crater. You need a sleeping bag, sunglasses, sunblock, hat, trekking shoes, rainwear, and warm clothes.
To get to El Altar volcano from Riobamba, take the road Riobamba-Banos to Penipe, about 22 km. Once there, head southeast to the village of Candelaria, 15 km drive down a dirt track. If going by bus, from Riobamba's terminal terrestre, buy a ticket directly to the Candelaria, a one-hour bus ride only available 3 times a week. Alternatively, you can get to Penipe on any of the frequent buses, once there, hire a truck from the main square.