Heritage Open Day: Step back in time and find out about Berwick in the past through our permanent and summer exhibitions. This year's main exhibition is 'Berwick's Bridges - a history of the present bridges spanning the River Tweed. In 1682 a Main Guard building stood in front of the Town Hall. By 1725, it had moved up Marygate to a site opposite Eastern Lane. However, complaints about its location led to a new Main Guard being built in 1743 in the area in front of the former Berwick Advertiser offices at the top of Marygate. It was then dismantled in 1815 and rebuilt on its present site in Palace Green. It contains two main rooms, one for the officer of the guard and the other for soldiers. Between them is a prison cell or 'black hole' where drunks and vagrants could be locked up.