This is Avenue Trianon, the big alley that links the Trianon Palace with the Versailles Castle. As you can see in the photo, distances are rather big. There is 1.5 km from here to the Chateau. The walk takes 25 minutes. With the mini train, it takes only a quarter of an hour.
If you like strolling, you should not miss this opportunity. A walk along these big avenues, will give you the chance to see some things you may miss with the "quick" train ...