More than half of Peru is covered by Amazon rainforest. The most practical way to add it to an Andes trip is through Puerto Maldonado, about an hour by air from Cusco, where lodges sit along the rivers of the Tambopata region.
Rainforest days start early and end with the sunset, so the Amazon pairs well with a slower stay in the Andes.
Tambopata National Reserve

Protected rainforest reached by boat from Puerto Maldonado.
Macaw clay licks
River banks where flocks of parrots and macaws gather in the early morning.
Lake Sandoval
An oxbow lake where giant otters, caimans and hoatzins are often seen.
Rainforest walks
Day and night walks with a naturalist guide, looking for monkeys, frogs and insects.