Afghanistan is at the cultural crossroads of Asia, where the great civilisations of Mesopotamia and Iran, South Asia and Central Asia overlapped and sometimes conflicted. Its landscape embraces environments from the high mountains of the Hindu Kush to the Oxus basin and the great deserts of Sistan; trade routes from China to the Mediterranean, and from Central Asia to the Arabian Sea cross the country. It has seen the development of early agriculture, the spread of Bronze Age civilisation of Central Asia, the conquests of the Persians and of Alexander of Macedon, the spread of Buddhism and then Islam, and the empires of the Kushans, Ghaznavids, Ghurids and Timurids centred there, with ramifications across southern Asia. All of which has resulted in some of the most important, diverse and spectacular historical remains in Asia.