A Cold War bunker near Brecon will open its doors to the public next month as part of a festival offering free access to historic sites across Wales.

The Brecon Royal Observer Corps Monitoring Post at Cefn Cantref will be open on Saturday, September 12, from 11am to 4pm as part of Cadw’s Open Doors festival.

Visitors will be able to descend 15 feet underground by ladder and explore the restored bunker, which has been returned to its original operational condition.

The post was one of more than 1,500 Royal Observer Corps nuclear monitoring posts across the UK, used from the early 1960s to the 1990s to monitor the effects of nuclear blasts and radioactive fallout.

The Brecon post has been restored to how it would have looked during the Cold War, with its communication equipment working to recreate the atmosphere in the lead-up to a nuclear conflict.

Former Royal Observer Corps personnel will also be on hand to share their experiences and explain the role they played.

Visits will take place in half-hourly tours, with groups of up to six people. Booking is required in advance.

Booking information can be found on the Cadw website.

Anyone visiting the underground post must be fit and able to use the ladder. Children under 12 can go underground with parental permission.

Open Doors returns throughout September, giving visitors free entry to hundreds of historic locations across Wales, including sites which are rarely open to the public.

Other attractions taking part across Mid Wales include Powis Castle and Gardens in Welshpool, which will offer free access on September 12 and 13.

The Old School in Whitton, home to the Museum of Welsh Textiles, will also take part throughout September, while Newtown Library will open its doors on September 8.

Powys Archives will welcome visitors on September 26, offering the chance to discover records covering centuries of history across Montgomeryshire, Radnorshire and Breconshire.

The Welshpool and Llanfair Light Railway will also take part on September 12 and 13, with talks about the railway and guided walks along its original route.

Open Doors is organised and funded by Cadw as Wales’ contribution to the European Heritage Days initiative.

Visitors are advised to check individual listings before travelling, as booking requirements vary between venues.