A local industrial estate isn't usually where you'd expect to find a fascinating historical gem.

But archaeology is all around you in Orkney, with ancient sites and attractions to be found almost everywhere. Hatston Industrial Estate on the outskirts of Kirkwall is no different, and tucked away in amongst its many businesses is the incredible Grain Earth House.

This subterranean structure was built during the Iron Age and possibly used to store food. From the outside it resembles a lot of Orkney's archaeological sites - it's a simple grassy mound - but once you open the door to the stairs below, you really feel like you're stepping into another era.

The earth house is around two metres under the surface, at the end of a five-metre-long curving passageway. The stone work throughout is exquisite and the main chamber itself is tall enough to stand up in, with its roof supported by four huge stone pillars,

The earth house was first uncovered in the early 1800s and shards of pottery, antler and animal remains were found inside. Other excavations in the nearby area have revealed other structures, so it could have been part of a wider settlement.

The Grain Earth House is one of those unique Orkney attractions. It's free to visit and open year-round. You have to pick a key up from the Judith Glue shop on Broad Street in Kirkwall to gain access, and do remember to bring a torch. Prepare to get your knees dirty too as it's a fairly snug fit. But you'll also get the chance to experience ancient Orkney with no queues, custodians or tickets - just open the door and travel back in time.

Find out more about Grain Earth House from the Orkneyjar website.

See more of our hidden Orkney attractions via our interactive map.