Ancient Empire :
1. Achaemenid Empire at its Greatest extent-8.0 million km sq. (480 BC)
2. Han Empoire, China - 6.5 million km sq. (AD 100) 
3. Roman Empire - 6.5 million km sq (AD 117) 
4. Macedonian Empire - 5.2 million sq. (323 BC)
5. Maurya Empire - 5.0 million kmsq. (250 BC)
etc....etc....etc