I recently came back from a week in Borneo. Having found myself in southern Asia on another adventure, I decided I needed to go to Borneo and visit the rainforest. While I was there primarily for the orangutans, we did see many other species from pygmy elephants to multiple types of birds.
Once there and after many disclaimers by our guide about how rare sightings of orangutans in the wild are, we saw our first one on our way to the lodge to start the visit. We were paused on the Kinabatangan River busy watching a group of proboscis monkeys when the guide pointed out a big male orangutan in the trees just a bit downriver. Those who had a very long lens or binoculars saw details as he was very high up and just a dark blob to the naked eye.