A day at Alton Towers isn't to be sneezed at of course, but sometimes you just want to root around a derelict military site from the second world war, or an ugly 70s pseudo-Corbusier monstrosity made by someone who hated humans. My idea of fun.
Here are some in this book which caught my eye: Imber - a village on Salisbury Plain which was taken over by the army in WWII and never handed back. You can still visit on a few days a year, and it looks like it's been preserved in the 40s, but also done up like a training level on Call of Duty.
Orford Ness sounds even better. It's a peninsula off the coast of Norfolk where they tested secret weapons, including components for the atomic bomb. There are big creepy pagodas dotted around which seem to be designed to collapse in on themselves if something horrible happens.
There are some cracking sights I've visited already in this book, from Portmerion to Avebury. It even has Tebay Services on the M6, which I visit (twice) every time I make a trip to Shrewsbury. The only motorway service station which doesn't make you want to kill everyone.
But the one place that intrigues me most is the Williamson Tunnels. It's a baffling, Escheresque labyrinth built under the streets of Liverpool by a rich nutcase two hundred years ago. Nobody knows what it was for or how far it stretches. It's currently being excavated by people who have clearly never read any HP Lovecraft.