The nationwide event sees castles, tunnels, city halls – and nineteenth century ironmongers – open their doors for a weekend of special tours and free events.

The Royal Liver Building is somewhere we pride ourselves on knowing pretty well. The Grade I-listed building has presided over Liverpool’s docks since it was built to house the headquarters of the Royal Liver Assurance group in 1911 and has become a trusted landmark for generations of sailors, shipyard workers and lost tourists. So iconic are the stone Liver Birds perching atop its clock towers that legend states the city will cease to exist should they fly away (don’t worry, they chained both down, just in case). But are we as familiar with the Liver Building as we like to think? Still a privately owned office complex, it is mostly off limits to the public and few have ventured much beyond its gleaming atrium.

As part of this year’s Heritage Open Days, the Royal Liver Building joins hundreds of other historic landmarks to invite visitors in for a special viewing. The nationwide event runs from 12–15 September and celebrates the country’s architectural treasures by offering free access to places normally closed to the public. Castles, city halls, tunnels and towers abandon the velvet rope – but it’s not just the architectural dons that get involved. The Open Days weekend also shines a light on overlooked areas of local history. JB Banks Ironmongers, for example, may not have the Liver Building’s world heritage status but its 177-year contribution to Cockermouth marketplace is no less impressive. It too asks visitors to come in for a look at the “back of the shop” this month.

JB Banks Ironmongers may not have its Scouse counterpart’s world heritage status, but it’s still impressive

The North West is well served by this year’s Heritage Open Days programme. Alongside (or should that be “underneath”?) the Liver Building, the Mersey Tunnel is open for a special tour, taking visitors through the inner workings of the city’s underground roadway. Queensway Tunnel’s ventilation system and headquarters, the George’s Dock Building also opens for a rare tour of its Art Deco interior. Away from the waterfront but no less nautical, Park Hospital stages a model boat exhibition and offers ghost tours of its Grade II-listed buildings. The nineteenth century hospital was designed by Alfred Waterhouse and housed the orphans of crewmen lost at sea for nearly 100 years. If you’re still searching for the elusive Liver Bird, St. Luke’s church supplies an exclusive look inside it’s bombed out shell – and a glimpse of what it alleges is Liverpool’s oldest Liver Bird.

What Manchester lacks in stone birds, it makes up for in stone churches. St. Philip with St. Stephen’s takes beyond the ballustraded parapet for a tour of its crypt. The church was designed by Sir Robert Smirke in 1825 and it remains one of the city’s only examples of Greek-style architecture. Salford’s oldest church, Sacred Trinity invites the “brave and the fit” to explores its hidden corners, while the Monastery in Gorton stages a photography exhibition in its Great Nave. The nineteenth century monastery housed Franciscan monks until 1989 and the Edward Pugin-designed church earned it a place on the World Monuments Fund Watch list (along with the nickname, “Manchester’s Taj Mahal”).

Venturing outside the city, the Merzbarn near Ambleside is an opportunity to learn more about German artist Kurt Schwitters, who used the barn to form his iconic sculptural artwork in 1947. “The Merzbarn” itself (the actual artwork once adorning an interior wall) has since been moved to Newcastle’s Hatton Gallery but the site remains a place of pilgrimage for those interested in the legacy of one of Modernism’s greatest exponents. In nearby Grasmere, the National Trust opens Allan Bank house and grounds. The Georgian villa was once home to William Wordsworth and has been left undecorated, allowing visitors to physically experience the many layers of history that make up its story.

This celebration of a building’s layers, however hidden they may be, sits at the heart of the Heritage Open Days scheme. It’s not often that we get the opportunity to peel them back – who knows what lies beneath.