These unconventional travel destinations are a far cry from the standard beach holiday. From a treehouse swaying in the canopy in Spain to a converted fishing boat in France, spend the weekend somewhere out of the ordinary.

A windmill in Greece
On the northeast coast of the volcanic island of Santorini lie three whitewashed windmills, their canvas sails creaking in the wind (from £225; each sleeps up to five; open from May to October). Designed and built by owners Nikos and Fotini, each has three storeys, with magnificent views of the Aegean Sea from the bedrooms on the upper floors. Much is made of the windmills’ curves – beds, staircases and bathrooms are built into the walls rather than fight against them. There’s little reason to leave your circular home with each boasting a private pool and a terrace, but there are plenty of beaches nearby, including Pori Beach with its unusual black sand.

A houseboat in Amsterdam
From hemp hotels to B&Bs run by former madams, Amsterdam is no stranger to the atypical lodging. A more salubrious take on the city’s clichés is a stay on a houseboat. Hundreds are moored within the inner circle of canals in the Dutch capital and, with costs rising, some are being turned into self-catering properties or B&Bs. Find an Amsterdam Houseboat lists 40 boats, ranging from the rustic to the space age. Favourites include the Prince Royal, with a bar built into the old wheelhouse and views of Anne Frank House (from £180; sleeps four), and a houseboat on the Prinsengracht, complete with sun terrace and roll-top bath (from £100; sleeps three).

A treehouse in Spain
The treehouse has undergone something of a renaissance in recent years, with canopy-level accommodation springing up all over Europe. Cabanes als Arbres takes things up a notch, with a veritable village of houses perched up in the branches of the Forest of the Guilleries in Girona (from £80). Each of the 10 cabins is built around a Douglas fir or beech tree and has its own terrace, perfect for a sunset drink with views of the surrounding mountains. To preserve the natural atmosphere of the woodland, there is no electricity – guests are warmed by a paraffin heater, can read by candlelight and hoist up their breakfast from ground level using a basket and a rope.

A spa hotel in Budapest
People have come to Budapest since Roman times to benefit from the healing properties of the thermal water bubbling up from the 118 springs beneath the city. And the very best way to enjoy that water is by staying at the Danubius Hotel Gellért, a huge Art Nouveau edifice on the banks of the Danube (from £85). Guests have direct access to the Gellért Spa and Bath, with its thermal pools decorated with mosaics, massage rooms and dry and steam saunas. Taking the waters in the main hall, under a galleried glass roof, has been likened to swimming in a cathedral. Rooms in the hotel are comparatively plain, but after all that therapeutic soaking you’ll be too nonchalant to care.

A thatched boat in Brittany
If the idea of a houseboat is just too passé, you could always head to France and stay in a fishing boat. With a thatched roof. Beached in the garden of a B&B nearly two miles from the sea. For that is what you’ll find in Kerlouantec, a small village on the Breton coast. La Caloge is an old seafarer converted into self-catering accommodation (from £85), with a bed built around the masthead and plenty of nautical details. The kitchen is in a fisherman’s cabin away from the sleeping quarters, and the owners will lend out bikes for excursions to nearby eateries.

A Scandinavian cabin in Wales
Things are getting groovy in the Teifi Valley in west Wales. Here, in a small woodland holiday camp, you’ll find Scandinavian-influenced Caban Casita (from £142 for two nights; sleeps two). Inside, flower-power cushions, a globe chair and pine cladding lend an Austin Powers vibe. There’s a kitchen, complete with 70s-style serving hatch, or you can head to The Nag’s Head Inn, a brewery pub serving local produce such as Teifi River trout and Welsh lamb. On a fine day, take breakfast on the secluded terrace then make the short drive to Cardigan Bay, with its miles of unspoilt coastline and Blue Flag beaches.

A prison in Lincolnshire
For more than 250 years, the small village of Folkingham in Lincolnshire was home to a house of correction – a form of prison used to re-educate the idle and disorderly. All that remains is its 19th-century gatehouse, now owned by the Landmark Trust (three nights from £337; sleeps four). The imposing exterior – meant to intimidate offenders as they were brought in – gives way to a cosy living room with open fire; a kitchen perfect for long, possibly disorderly dinners; and two bedrooms on the upper floors. Those on day release should escape to sea and take a boat into the Wash estuary for a bit of seal-spotting (£18).

Auntie Beeb’s old home in Evesham
Wood Norton has had many incarnations. The estate dates back to medieval times but the current hall is a Victorian country house remodelled by the Duc d’Orleans, pretender to the French throne. The BBC took over the building in 1939 and used it as an emergency base during WWII. Since then, it has been used as both BBC training centre and Doctor Who film set. Its latest guise is as a luxury hotel (from £85). Be sure to ask for one of the rooms in the main hall, which with their oak panelling, fat mattresses and roll-top baths evoke Wood Norton’s days as a stately pile.

A river lodge in Portugal
Deep in the São Mamede Natural Park in the Alentejo region of Portugal lies the Moinho do Pego Ferreiro, an abandoned mill restored in 2006 by British couple Cathy and Richard. A river runs through the smallholding, swathed in olive, cork, walnut and fig trees, and it’s here that you’ll find the River Lodge, a wooden platform covered by canvas and home to a double bed (from £35; open April to October). There is nothing here to distract from the art of simple living. So light a camp fire, take a dip in the river, watch for otters or freshwater turtles and enjoy the seasonal produce (including homemade beer) made on the premises.

The article 'Nine unusual places to stay' was published in partnership with Lonely Planet Traveller.