Christopher Reeve's son, Will, has a new doc dropping -- where he travels to all the places his dad visited around the globe ... and the journey's made him feel closer to his father.

TMZ caught up with Will ... and he tells us he literally followed in the footsteps of his iconic "Superman" dad -- hitting spots from a tiny Alaskan village to a remote lagoon in Mexico, even linking up with the sons of the men who guided Christopher back in the day for the full experience.

Will tells us the ABC doc "Will Reeve: Finding My Father" has been years in the making ... driven by his desire to experience the adventurous, action-packed life his dad lived before a horse-riding accident incapacitated him.

Catch the video -- while Will's all smiles, and you can tell it's an emotional ride ... as he opens up about wanting to connect with a version of his dad he never got to know, since his dad died when Will was young.

The doc's releasing February 26, and he shares what filming it was like for him, and how he's stoked about the bonus perk -- tons of Sky Miles from all the travel!