Founded in 1895 to safeguard places of historical and natural beauty throughout England, Wales and Northern Ireland, the National Trust now looks after more than 500 properties, many of which you may never have heard of. (Scotland also has its own National Trust, established in 1931.) Until 30 November, National Trust is offering one free ticket per household (up to two adults and four children) to sites that usually charge entry. Just show your ticket at the site of your choice – but check which properties are exempt before you set off. Some are quirky, some are creepy, but all are equally fascinating.