Leptis Magna is arguably the best-preserved Roman city in the world — better than Pompeii in scale and completeness, if not in the preservation of its organic daily life. The city was founded as a Phoenician settlement in the 7th century BCE, grew under Carthaginian control, and reached its zenith under Roman rule after the 1st century CE. What you see today — the harbour, the market, the forum, the amphitheatre, the baths, the triumphal arch of Septimius Severus — is an almost complete urban layout extending across a large site overlooking the Mediterranean.
The site requires a full day to do justice. Key structures include the Severan Forum and Basilica (one of the grandest public spaces in the Roman world), the massive public baths of Hadrian, the theatre, and the circus along the seafront. The market has intact measuring tables for trading. The UNESCO designation is well-earned. Arrive early in the morning — the heat on the white stone is fierce by midday in summer, and the light for photography is best before 10am.