Obscura Day is a holiday that never occurred to me, but it absolutely perfect. From their website:
Obscura Day is an international celebration of unusual places. It is a day of expeditions, back room tours, & exploring hidden wonders in your own hometown.
On Obscura Day thousands of people, all over the world, go out and explore interesting and unusual places. Sometimes we organize the event, sometimes folks organize it themselves! Over the past two years nearly 10,000 people have attend over 200 different events on Obscura Day.
Obscura Day is on Saturday, the 28th of April, just two weeks from now. There are four official events being held in Philadelphia, at Eastern State, the Art Museum, Mount Pleasant Mansion, and Laurel Hill Cemetery. All of these events will cost you something, but there are loads of free things you can do that hold to the spirit of the day. In some ways, I would actually say that the things you can do by yourself hold more to the spirit of the day, since they’re more likely to be off the beaten path than, say, Eastern State, which pretty much everyone in Philadelphia has at least seen from the outside.
That said, I would rather fancy having a tour around Chislehurst Caves, southeast of London.
Who knows, maybe I’ll have an Obscura Day adventure myself and post pictures here. If you know a site that you’ve always meant to explore but could never quite make the time, take the upcoming holiday to have that adventure, and please, take some pictures so you can share your adventure with others.