Having tried in vain to identify the location of a series of photos showing a castle, and only coming up with that it must be in the UK (building style, amount of clothes people were wearing, tulips coming out), but a Google image search on “UK castles” not being helpful, I discovered that Google can do a “reverse” image search.
Just go to https://images.google.com, click on the camera icon, then “Upload an image”, and let it have a go. Just a few seconds, and it came up with the result: it turned out to be Arundel Castle.
It does seem to give good results for popular touristy places (London and Paris certainly), but not so with more “off-the-track” places. Still, I’m quite impressed by it.