Causeways, those paths that appear and disappear with the washing in and out of the tide, are places of uncanny mystery – it’s no wonder a tidal island has been used to conjure up strangeness in the Jude-Law-helmed folk horror series The Third Day.

Right now, we are in a wave of COVID-19 restrictions, but that tide will pull back, an we can dream or plan, or even visit a local causeway. There are 17 tidal islands that can be walked to from the mainland of Scotland, and still more from the isles themselves. These are islands you can walk to - neither one thing nor the other, half mainland, half island. On a visit to them there is always the possibility of getting stranded, of finding yourself trapped. There is never not that thrill of the clock ticking. Don’t chance it – always stick to the safe crossing times.

Five Scottish harbours we can't wait to revisit

Cramond, Edinburgh

The mile-long path that takes the visitor out to this grassy island in the Firth of Forth, is unmissable and impossible to stray from since it is lined with a string of tall and imposing, jagged concrete teeth. These were a submarine defence boom constructed during the Second World War to stop vessels passing on that side of the island. On the island itself there are plenty of other signs of its requisitioning during World War I and II, and use as part of the defences - it is littered with ghostly former military buildings, bunkers and emplacements, some scrawled with graffiti. It’s not uncommon for visitors to get stranded by the incoming tide, so check online before hand and also on the noticeboard at the mainland end of the causeway with times when it may safely be crossed.

Oronsay, Skye

The name of this uninhabited island is derived from the Scottish Gaelic word ‘orasaigh’ which means island of low tide. A pebbly causeway, covered during the hours around high tide, takes the hiker across to this wild, uninhabited island of rugged cliffs, in the waters of Loch Bracadale. There is a cave and an arch to explore on the south shore. Oronsay is one of a number of tidal islands off Skye – there is even another with the same name – and a popular hiking destination.

Davaar, Kintyre

They call the path across from the mainland to Davaar island, the Dhorlin. It’s a natural shingle causeway which is revealed at low tide at the mouth of Campbletown Loch off the east coast of Kintyre. Once known as Sant Barre, Davaar houses a Stevenson lighthouse at its northernmost tip as well as a converted naval building which is now a holiday home. The island is also residence for sheep, goats and mink. However, what it’s most famous for, though, is the cave with the crucifixion painted in 1887 by local artist Archibald MacKinnon after he had a dream. A crossing of the causeway takes around 40 minutes, though it might take you longer if you pause for a while to watch the gannets, travelling from Ailsa Craig, swooping and diving for fish.

Eilean Tioram, Lochaber

When Loch Moidart tides are low, walkers can reach the island of Eilean Tioram and its ruined Castle Tioram, by taking the stone causeway out into the loch. The castle and its island once controlled access to Loch Shiel, and was the traditional seat of the Clan MacDonald. It’s now a romantic, haggard ruin, clamped over the granite summit of the island. Follow the circular walk that starts from the former settlement of Scardoish or, for a longer hike, take the Silver Walk. This route takes its name from a gruesome and haunting tale associated with the island – that of a girl who was accused of stealing silver from the castle and hiding it along the route. She was taken to rocks to the north of the castle, tied by her hair, and left to drown in the rising tide.

Brough of Birsay, Orkney

Off the north-west of Mainland Orkney, this uninhabited tidal island, which boasts the remains of Pictish and Norse settlements. People lived here from the 7th to the 13th century AD and there are remains of settlements and a 12th-century monastery. Your path across the sands is via an, often slippery, concrete causeway around 150m long. Take care. Access the the Bough of Birsay is only possible within two hours either side of low tide. Don’t attempt to cross when the causeway is submerged as the tides here are strong.