Petra is the name of the huge Nabatean and Roman archaeological site, whereas Wadi Musa is the name of the town where the site is.
Head down the claustrophobic confines of the siq for your first glimpse of the Treasury, featured in Indiana Jones and the Last Crusade; hike to the High Place of Sacrifice; wander amongst all the rock-cut tombs; and climb up to the Monastery for the incredible views.
You can ride a camel or a horse, check out some well preserved Byzantine mosaics, visit the site by candlelight, and even have a drink in a cave.
Described as "a rose-red city half as old as time", and made a UNESCO World Heritage site in 1985, Petra is a place that really does live up to all the hype.