When it's finished, it'll be the tallest skyscraper in South America. But despite its mammoth size, few people will work or live inside it.

Instead, the Amazon Tall Tower Observatory, which is nearing completion in the middle of the Amazon rain forest, will gather data on gases like carbon dioxide, methane, and other components of pollution to help scientists better understand what is happening to our climate.

It could also help us answer a key question about the rain forest's relationship to CO2.