If you want a holiday in a pigsty...

...you'll need to consult the Landmark Trust, the charity that rents out whacky buildings.

Who in their right mind would want to holiday in a hospital, take a break in a blockhouse or in a house of correction? In a pigsty or in a pineapple? Down a mine or up a water-tower?

Since we began renting holiday accommodation from the Landmark Trust two and a half years ago we've stayed in six such buildings, looked at a further six, and have just booked up for our seventh. These architectural gems had all fallen into disrepair but were rescued, repaired, renovated and refurbished by the Landmark Trust, which has just celebrated its 30th birthday. This architectural charity offers self catering holidays in addresses to die for - castles and chateaux, priories and palaces, chapels and colleges, abbeys and an Admiralty Lookout, manor houses, banqueting houses and gatehouses, a Government House and a "White House".

Our very first Landmark experience was the Martens Tower at Aldeburgh in Suffolk. Short and squat, it stands four-square on the sea wall, the largest and most northerly of the chain of towers put up to keep Napoleon out. Built in the shape of a quatrefoil for four heavy guns, it is made up of nearly one million bricks and looks like a gigantic sandcastle. There's a drawbridge and half a moat (the other half having disappeared into the sea) while up on the flat roof, from which guns were once fired, you can gaze up at the stars.

Our second was the Gothic Temple at Stowe in Buckinghamshire and our very first sighting of it was through a grey November mist. Standing on high ground, surrounded by sheep, this imposing triangular temple of red sandstone was built in 1741 and is one of the last additions to the garden formed for Lord Cobham of Stowe.

We took yet another tower for our third "Landmark". Luttrell's Tower at Eaglehurst near Southampton is tall and elegant, standing on the shores of the Solent looking towards Cowes. It was used by Marconi for his wireless experiments in 1912 and is an exceptionally fine Georgian edifice with spectacular views from the top floor living room of ships entering and leaving Southampton.

Next was a castle, an awe inspiring experience and far from run-of-the mill self-catering. Clytha Castle is a Georgian hilltop folly overlooking the Vale of Usk in the Welsh Marches, surrounded by ancient war-torn ruins of real castles such as Raglan and Chepstow, Grosmont, Skenfrith and White, Tretower and Caerphilly. Leased from the National Trust, it stands on the edge of a grove of old chestnuts, fronted by a ha-ha to keep out the sheep which graze on the slopes below.

It was then off to hospital - Beamsley Hospital near Skipton in Yorkshire, a single storey circular stone building that was built as an alms house in 1593. It had rooms for seven women, encircling a chapel, through which most of them had to pass to reach their doors - a daily encouragement to piety. Until the 1970s the little community of Mother and Sisters lived here, their lives governed by ancient and ferociously strict rules. Using its oddly shaped rooms and repeatedly crossing the chapel was a curious experience.

It is always exciting the first time you turn the front-door key of a Landmark property, not knowing quite what to expect. Seeing pictures in the handbook is not the same thing as actually setting foot inside one of these weird and wonderful buildings. And our last folly to date, Tixall Gatehouse, was no exception. Built in 1580 by Sir Walter Aston to stand in front of an older house which has since disappeared, it is a magnificent Elizabethan structure deep in the heart of Staffordshire. Standing alone on high ground, stark grey and four-square with a turret in each corner, it is said to have a ghost. We thought said ghost might be Mary, Queen of Scots, who was imprisoned here for two weeks in 1586.

The property was bought by the trust in 1968 for pounds 300 and was one of the very first historic buildings they rescued and restored. Today the roof is paved with stone and from here, surrounded by balustrades and turret tops, there are wonderful views over the parkland (landscaped by Capability Brown) down to the canal where a section has been dug out to form a lake known as Tixall Wide.

In one of the turrets lives the gatehouse clock. It is locked away since it has no hands or face. To show this is of no matter, the working mechanism merely strikes the hour and half hour which it does with perfect precision. Wake up call at Tixall is 7am sharp but happily there's a timing device so that the clock doesn't strike between the hours of 11 and seven.

To book a property you need the Landmark Handbook. It costs pounds 8.50 (inc. p&p - cost refundable against booking) from The Landmark Trust, Shottesbrooke, Maidenhead, Berkshire SL6 3SW (01628 825925). Prices vary according to property and season. Midwinter short stays (four nights Nov-March) are the cheapest and for Clytha Castle, Beamsley Hospital and Tixall Gatehouse prices start from pounds 403, pounds 266 and pounds 364 respectively.