While some people were Instagram-ing their lunches, Twitter founder Jack Dorsey was live-Vine-ing his ascent to the top of the San Francisco-Oakland Bay Bridge. Just another day at the office.

Here’s his incredible, heart-pounding climb and descent, six seconds at a time. Warning: If you don’t like heights, this one’s not for you.

See Dorsey’s Twitter feed for more amazing Vines from his adventure.