The Ruta de la Cascadas near Baños in Ecuador is a pretty scenic ride along the mountains. We rented bikes for the day and rode part of the 62km route down to Puyo. They tell you it’s mostly downhill but it’s also uphill for quite a stretch ;)
The road however is very very beautiful with cascades all along. Densely forested mountains, waterfalls and a river to ride by. Pure heaven!