evidence: Written history in Ireland began with the introduction of Christianity. Before that time information was handed down using oral tradition. Archaeologists have used the evidence of stray finds and excavations to piece together the prehistory of the Lagan Valley. The area would have been very attractive to settlers: the fresh water of the river, the low-lying areas close by and the hills beyond. A Google map showed the area. On the western side of the valley lay the steeper hills which were later to provide the fast-flowing streams needed by the linen industry. On the east the land rose more gradually to form the Castlereagh Hills. We were shown several views across the city to the hills on both sides. [...] The next period discussed was between 10,800 and 10,000 years ago. During this time there was a cold snap when the ice sheet advanced once more. The Lagan valley escaped this, but some geologists have suggested that ice blocked the Lagan and a lake was formed. Water then possibly flowed out through the Dundonald gap towards Comber and Newtownards. The temperature then began to rise again and trees spread until the country had much more woodland than today. Forest animals thrived and finally man arrived.