Palmyra is a desert oasis and ruined city in the centre of Syria. It was founded in the 2nd Millennium BC but didn't become one of the greatest cities of the ancient world until the 1st century AD. At this time it usurped Petra in Jordan as the major trade city on the caravan routes between Persia, India, China and the Roman Empire. Much of the remaining architecture is Roman with a 1,100m long colonnaded avenue at its centre. Important buildings include the agora, forum, Temple of Bel and theatre. Nearby are 200 funerary towers and tombs from the Hellenistic and Roman periods.
This image shows some of the columns along the main colonnaded avenue. I visited in summer 2009 before the Arab Spring of late 2010. Unfortunately, videos posted on the internet seem to show Syrian soldiers looting these ruins.