IF you're looking for something to do this weekend, why not take a day trip 2,000 years back in time?

You could visit the 'thorny fortress' in Oxford where St Frideswide sought refuge in the eighth century, explore the Iron Age 'Cassington Ring' discovered by aerial photography, or conquer the once-mighty Letcombe Castle near Wantage.

For the first time ever, Oxford University has helped reveal the locations of these and 4,144 other historic hillforts across the UK in a free and easy-to-use online map.

The interactive website, compiled with help from Edinburgh University and University College Cork, was funded by the Arts and Humanities Research Council and includes some 40 ancient sites right here in Oxfordshire.

Oxford professor Gary Lock said he and his team wanted to create the tool just as much for ramblers, cyclists and history enthusiasts as much as academics.

He said: "It is important that our online database will be freely accessible to all researchers and interested parties.

"We hope it will encourage people to visit some incredible hillforts that they may never have known were right under their feet."

Mostly built during the Iron Age, the oldest hillforts date to 1,000BC and the most recent to 700AD.

Among the local treasures is Thornbury, just off the Botley Road at Binsey.

Located around St Margaret's Chapel, this site is almost certainly the same Thornbiri (meaning 'thorny fortress') named in the 12th century Life of St Frideswide as one of the last places she sought refuge from the ruthless Mercian king Æthelbald who was hell-bent on marrying her.

It was at Binsey that St Frideswide is supposed to have prayed to God for a well to spring up from the ground to stop the local nuns having to walk so far to get water.

Excavations in the 1980s found Anglo Saxon pottery on the site but its use is believed to date back to the Iron Age.

Ilbury Camp, halfway between Oxford and Banbury, was mentioned in the Domesday Book commissioned by William the Conqueror in 1086.

Today, the hilltop north east of Nether Worton offers fantastic views across the Cherwell Valley, and Iron Age pottery has been discovered right on the surface.

One of the most famous sites on the map, though, is Uffington's White Horse Hill.

As well as hosting the world-renowned Bronze Age chalk carving, the hill itself was used as an Iron Age fort.

The so-called ‘castle', which occupies the summit, dates back to the eighth century BC and is described by English Heritage as 'a rare and outstanding example' of the genre.

More historic forts can be found at Oxford and across the county by browsing the online map at hillforts.arch.ox.ac.uk