World's Most Secret Hotels

Unusual destinations featured in this episode include a mountain retreat at the summit of Mount Pilatus in Switzerland, and a striking Brutalist hotel that transformed concrete into an architectural masterpiece. Off-grid in the English countryside, two handcrafted geodesic pods offer the ultimate digital detox, while a working lighthouse on La Palma secretly houses a luxurious hotel.

Featuring a South African nature reserve, Classic railway carriages repurposed as a luxury hotel in Kent, and curious submarine accommodation in the Scottish Highlands. An old freight crane is reborn as a harbour-side hotel in Hamburg, and there's a retro retreat in Utah, featuring wagons that never roll.

In the Bradshaw Mountains in Arizona, USA, hidden down an 11-kilometre dirt road, is a luxury hotel built around a geothermal wonder. At The Bus Stop in Scotland, there are nine luxury buses for hire, while a secret retreat in Poland has been designed to look like an open chest of drawers. Plus, a one-of-a-kind glamping pod in eastern England, and a boutique bolthole inside an ex-windmill in Suffolk.