More than a million people flock to the monument in Wiltshire each year, with hundreds attending ceremonies to mark the solstices.
Since the end of the 19th century, Stonehenge has been "severely compromised" by the intrusion of roads and traffic, with outdated visitor facilities.
A section of the A344 road was permanently closed in June and tomorrow the visitor building will open.
The centre, designed by architects Denton Corker Marshall, lies a mile-and-a-half to the west of the stones.
Tourists able to use a 10-minute shuttle bus or walk down a newly-reconnected ancient approach.The transformation is the largest capital project ever undertaken by English Heritage.