SOUTHAMPTON'S most historic buildings are opening to the public free of charge this weekend, as part of the national Heritage Open Days.

Until Monday, visitors to the city and surrounding area will be able to explore and enjoy guided tours of some rare architectural sites.

God's House Tower, housing the Museum of Archaeology, will be open with access to its roof, which features spectacular views of Southampton Water.

The medieval vaults buried beneath the modern city are to be opened up for special guided tours during the afternoon today and tomorrow.

There will also be guided tours of the house and grounds of Edwardian Townhill Park House, which was built in 1910 for Lord Swaythling and is now home to the Gregg School.

Britain's maritime history comes alive at Calshot Castle, a coastal fortress built by Henry VIII.

Just outside the city, guides will show visitors around the ruins of Netley Abbey, a 12th century Cistercian monastery, which was a popular destination in Georgian times for authors and artists such as Jane Austen and John Constable.

Heritage of a different kind can be found at Botley Mills, an 18th century water mill currently being restored as a Museum of Flour Milling, and at Bursledon, where the historic windmill is open on the weekend afternoons.