The creation of cairns and Megalithic monuments continued into the Bronze Age, which began in Scotland about 2000 BC. As elsewhere in Europe, hill forts were first introduced in this period, including the occupation of Eildon Hill near Melrose in the Scottish Borders, from around 1000 BC, which accommodated several hundred houses on a fortified hilltop. From the Early and Middle Bronze Age there is evidence of cellular round houses of stone, as at Jarlshof and Sumburgh in Shetland. There is also evidence of the occupation of crannogs, roundhouses partially or entirely built on artificial islands, usually in lakes, rivers and estuarine waters.