The Cotswolds  refers to a region of gentle hill country in south central England, the main range reaching 300 m (1000 ft) in altitude at its highest. The Cotswolds lie across the boundaries of several traditional English counties: Gloucestershire enjoys by far the largest portion of the region; the county shares this honour significantly with Oxfordshire and south Warwickshire, and to a lesser extent with Wiltshire, Somerset and Worcestershire.
Officially designated an Area of Outstanding Natural Beauty in 1966, in recognition of their unique appeal and the beauty of its predominantly rural landscapes, the Cotswolds are known worldwide for their stone-built villages, historical towns, and stately homes and gardens. Many consider the Cotswolds as representative of the archetypal English landscape, within easy striking distance of London and several other English urban centres.
The Cotswolds run generally south-west to north-east, the northern and western edges marked by steep escarpments down to the valleys of the rivers Severn and Avon and the city of Gloucester, the eastern boundary by the city of Oxford (the university "city of dreaming spires"), the west by Stroud, and the south by the middle reaches of the Thames Valley and towns such as Cirencester, Lechlade and Fairford. Key physical features of the area, including the characteristic uplift of the 'Cotswold Edge' can be clearly seen as far south as Bath.
The Cotswolds characterised by attractive small towns and villages built of the underlying rock, known as "Cotswold Stone" (actually, a yellow oolitic limestone).
During the Middle Ages, the Cotswolds became prosperous from the wool trade with the Continent. Much of this wealth was directed towards the building of churches, the area still preserving a large number of large, handsome Cotswold Stone "wool churches". The area remains affluent and has attracted wealthy Londoners and others who own second homes in the area or have chosen to retire to the Cotswolds.
Typical Cotswold towns are Broadway, Burford, Chipping Norton, Cirencester, Moreton-in-Marsh and Stow-on-the-Wold. The Cotswold town of Chipping Campden is notable for being the home of the Arts and Crafts movement, founded by William Morris at the end of the 19th and beginning of the 20th centuries. William Morris lived, occasionally, in Broadway Tower a folly now in country park.
The Cotswolds are home to a number of important historical houses, often set in their own estates and therefore not part of any particular town or village.
The local tourist board provides information on important houses open to the public, which include Snowshill Manor, Chavanage, William Morris's house at Kelmscott, Sudeley Castle and Berkeley Castle. Some houses are closed but provide the setting for nationally important gardens such as Hidcote Manor, Painswick Rococo or Abbey House Gardens. Gardens also described at 
Chastleton House  - maintained by the National Trust since 1991, when it was acquired from the last representative of the family who had owned the house since it was first built. Chastleton House is one of England’s finest and most complete Jacobean houses, filled not only with a mixture of rare and everyday objects, furniture and textiles collected since its completion in 1612, but also with the atmosphere of 400 years of continuous occupation by one family. The gardens have a typical Elizabethan and Jacobean layout with a ring of fascinating topiary at their heart and it was here in 1865 that the rules of modern croquet were codified. Since acquiring the property, the Trust has concentrated on conserving it rather than restoring it to a pristine state.
The Cotswolds  attracts people with a visual appeal derived from a long history and the charm of hundreds of honey colour stone villages spread over an area approximately 100m (160km) north to south and 50 miles east to west.
Whilst lacking a single large attraction or theme park, the Cotswolds is a wealthy area that nevertheless retains something of the appeal of a working environment. For visitors, the area is particularly well known for historic gardens, pubs and inns, farm and outdoor attractions and retail - book and antique shops especially. There is also a thriving arts and crafts scene, drawing on a legacy that includes William Morris but also extends to new artists at work in hotspots such as the Stroud Valleys.
The Cotswolds also has a strong food culture with frequent Farmers' Markets, local organic producers and individual businesses such as bakeries and orchard drink producers. The area has a long history of hospitality since being adopted by Londoners with newly available reliable motor cars a hundred years ago and there remains a concentration of high quality hotels and B&Bs in the area.
Cotswold Water Park, . Great Britain's largest water park consists of 133 lakes which were formed by filling old gravel quarries. It is located about five miles south of Cirencester in the centre of England and offers many water sports and activities.
Although this is central England, you may find locals speak with a heavy Gloucestershire accent although equally the area has a high % of RP residents from London and the South East - it's not known as 'Poshtershire' for nothing.
As you'll find all over Great Britain the cost of public transport is high (compared to mainland Europe, Asia, Africa, etc...). People under 25 can buy a Young Person's Railcard. This gives you 1/3 off standard rail fares, but costs £25, so it might only be worth it if you're planning to spend a long time in the UK. Railcards can be bought from any train station ticket office. You'll need a passport photo and proof of your age.
Trains do exist between some main towns, but the line from Cirencester was axed 30 years ago.
As Bill Bryson said, this is the only option to see the Cotswolds. He was probably right. It's great walking country though - gentle hillsides not mountains.
Note: Take care on commons of the cows (they stand/lie in the roads at night time).
The bus services in the Cotswolds are very limited, although the first time visitor might have some luck exploring the Fosse Way by bus - a Roman road connecting Moreton in Marsh and various market towns to Cirencester. Research is definitely needed. Many villages only get one bus a day, or some only one bus a week. Even larger towns, such as Cirencester and Stroud, only get one bus every hour.
The Cotswolds are hilly but there are well-marked cycle routes on quiet roads.
Look out for Double and Single Gloucester (and up to 100 other) cheeses, Old Spot Pork and local organic game and venison - plus soft fruits in season. Farmers' Markets here are well established and the local food culture is extending to pub noticeboard menus.
Donington Ale in the north Cotswolds.
The area is very safe, with little crime. (The headlines of the local newspaper a few months ago read "Butterfly found in carpark").