Castleton is one of the most popular villages/small towns in the Peak District - the UK's oldest national park which was established in 1951. The area is a mecca for walkers with no need for the car during your stay - there are literally hundreds of miles of footpaths accessible from the door - within a minute or two you can leave the village behind by heading up Cave Dale and out into the hills beyond - and what hills they are. Mam Tor, Rushup Edge, Lose Hill, Win Hill, Back Tor and last but not least the Kinder Plateau scene of the Mass Trespass in 1932 which was the forerunner of public rights of way and footpaths across the country.
Good pubs in Castleton include the Peak Hotel (under new management and doing very well for food and drink), turn right from the market square and follow the bend around for 2 minutes, with several others close by as well as many cafes, takeaways and restaurants too.
Famous places to see in Castleton include the show caves - Blue John, Speedwell, Peak Cavern and Treak Cliff cavern and a brand new (for 2018) Visitor Centre with masses of information about the area. Further afield the Peak District offers the amazing Chatsworth House, Haddon Hall (best-preserved medieval town in England), the 'pudding town' of Bakewell, the 'plague town' of Eyam (pronounced 'eem'), a scenic rail journey on the Manchester to Sheffield line - nearest station at Hope. Take the train from Hope to Edale (start of the Pennine Way) which is less than 20 minutes in length, explore Edale (2 pubs and a cafe) and its surrounding hills with access onto the Kinder Plateau or simply take a picnic and relax by the river Noe.
With so much to see and do in and around Castleton a week is the least you'll need to fully appreciate everything on offer but a short break is better than nothing so, whichever you choose, have a wonderful holiday in this beautiful part of the world.