Wearing a white shirt, khaki trousers and a cap, the first lady walked part way down the picturesque narrow canyon leading to the old city and its monumental treasury building made famous in the 1989 movie "Indiana Jones and the Last Crusade."
Photographers were forbidden to take shots of Mrs. Bush later riding a camel up the more than 1,000 steps to an old church built on a hilltop near the site.
The visit to the ancient city built by the Nabateans came at the end of a Middle East tour which took the first lady to the United Arab Emirates, Saudi Arabia, Kuwait and Jordan mainly to promote awareness of breast cancer, a taboo subject in the region.
She arrived in Jordan on Thursday where she was whisked from the airport to meet Jordan's ruler King Abdullah II who praised her efforts to raise awareness about the disease.
Following the talks, Mrs. Bush launched a breast cancer screening clinic at the King Hussein Cancer Center. The facility was named after Abdullah's father, who died of cancer in 1999.
The first lady announced that the U.S. Agency for International Development will disburse $225,000 (EUR158,000) for breast cancer screening as part of her campaign to expand the activities of a U.S.-Mideast partnership to fight breast cancer.