Despite no evidence of Iron Age occupation in Wrexham, good examples of hill forts are at Ruabon and Gwersyllt.
The Romans came to Britain in 43 AD and spread rapidly across the country, setting up the fort of Deva (Chester), tile-works at Holt, Wrexham, and a variety of small forts and camps linked by a sophisticated road system. No-one suspected Roman occupation in Wrexham until a coin hoard was unearthed during the construction of Sainsbury's supermarket at Plas Coch in 1991. All the coins mysteriously vanished!
It wasn't until the grass and topsoil was being stripped for the nearby Aldi store, in 1995, that actual Roman remains were found. The archaeological dig revealed trenches, stones, a hearth, corn drying kiln and some field boundaries. The site suggests a larger community, possibly a village.
The Romans departed in 410 AD, leaving Britain in the Dark Ages with tribal warfare and various invasions from Europe, including Danes and Vikings. Independent 'kingdoms' were established (Wessex, Mercia, Northumbria, etc), merging and separating in political and military dominance.
Offa's Dyke, built between 757-796 AD, runs from Prestatyn to Chepstow, a distance of some 180 miles delineating the political frontier between Mercia (ruled by the Saxon King Offa) and Wales (then occupied by various tribes of original Britons). It also formed a significant defence of ditch (on the Welsh side) and bank (on the eastern side), being some 60 ft wide overall and 15-20 ft high from ditch base to bank top.
Wat's Dyke, clearly seen alongside the motte and bailey at Erddig, lies further to the east and runs through the centre of Wrexham. There is currently some dispute whether it pre- or post-dates Offa's Dyke (at either 700-750 AD or 800-850 AD). Both dykes still define 'ward' boundaries and, indeed, the old Wrexham Borough boundary.
Following the Norman Invasion of 1066, Saxon lands were confiscated and the feudal system introduced. Fortifications were built - 'motte and baileys' by the earls and barons, 'moated halls' by the yeoman farmers.
The Mediaeval field system at Commonwood is a superb example of 'strip farming', each section being one furlong long by one chain wide (1 acre). A furlong was the distance a team of oxen could pull a plough without stopping, and a chain width (66ft), the amount they could plough in a day. So Wrexham has all its history beneath its feet! 
