I'd definitely agree with Greece in response to the original post, but that seems to be a given, so I'll consider the second best!EGYPT was a very inward-looking civilisation for most of its history, so it's not clear how much of an impact it had in its day. Nevertheless, it's architectural and artistic achievements, on their own terms, remain incredible, and both Greece and Rome were deeply inspired by their vision of Egypt, however romanticised and misled their vision might have been!PERSIA was significant for the political unity it brought to the whole Middle East region, and for giving us the Cyrus Cylinder, a very early declaration of human rights. On the down side, it was a very derivative civilisation, taking much of its iconography, organisation and art / architecture from earlier Mesopotamian powers.SUMER gave us civilisation. (Unless you're one of the growing number of archaeologists who believes the Harrappan civilisation of Pakistan got there first!) Also the first literature (the earliest stratum of Gilgamesh is Sumerian). All taken together, I'll go for Sumer!