Located two hours from the border crossing in Eilat, Petra is the premiere tourist destination in Jordan. Carvings from various historical periods may be seen there.
It is highly recommended that you go with a guide. However, if you do not, be careful: Petra was re-discovered only recently, and the people that lived there, the Bedouins, struck an arrangement with the foreigners who wanted to show the area off to tourists. Only the Bedouins would only be allowed to sell inside the city, their shops would not be interfered with, and they would take a portion of ticket sales. In return, they agreed to move out of the city.
As a result, Petra is extremely touristy in that as soon as you step inside, men aged five to fifty will attempt to get you to buy their wares, ranging from donkey rides to bangles to food. You can partake, but beware that tips are expected for most services, and the Bedouins will be aggressive in trying to get you to buy their wares. Be advised that it is free to get on a horse or a donkey or a camel, but it is not free to get off-- the person who guided you onto the animal expects a tip at the end of the ride.
At the Treasury, plenty of young men will offer to take you to the top in order to get a better view of the Treasury. This is incredibly dangerous and illegal.