Follies are wonderful things. I have great affection for those weird and wonderful buildings that people had built in olden days. They serve no purpose, other than being interesting to look at. Some contain steps that allow you to climb them. Many are in areas of great beauty and are often high above the surrounding landscape.
As trig points are often located close by I have included those that I have been fortunate to visit over the years. A useful resource for finding trig points can be found here: http://trigpointing.uk/
Also included are bridges, modern sculpture and other buildings that, whilst not follies in the true sense, are nevertheless interesting to visit.
Cromlechs are great things to visit. They are ancient burial mounds from pre-historic times. One wonders how the stones were placed without modern machinery.
Finally also included here are Lighthouses. Folly-like, but serving an essential lifesaving purpose.