Research is one of those indispensable features of writing that either drive you mad or make you waste an entire afternoon saying "Wow! That's neat!" For me, at least, one bit of information makes me look for another, and by the end of it, I am far, far away.
Anyone who writes historical fiction knows how crucial research is to the finished product. If the information is available, it needs to be heeded. If it is not available, then some careful thought is required. Even if you are inventing worlds, or countries with their own histories, you have to have some notion of the flow of time and the development of the civilization that you are dealing with.
Sometimes you can get tripped up rather spectacularly, as I discovered while I was writing the first book of my French series, THE ORPHAN'S TALE, set in Paris of 1834. I love maps, and I consult them very carefully when I am writing. I had some beautiful maps of Paris, which I pored over as I wrote.
...and then I discovered that all was in vain. First of all, it seems to be the normal thing in Paris to rename streets on a regular basis, depending on which person the government wishes to honor. As a result, I had Paul Malet, the hero of the series, crossing a square that led to the flower market, named for a Parisian Prefect of Police who served around 1890. In one scene, baffled and embarrassed, he stormed across the Place Andre Honnorat, named for a politician who lived between 1858 and 1950.
Add to that the fact that Napoleon III effectively tore Paris apart in the middle of the 19th century, altering the courses of streets, tearing up structures and making it difficult to figure out what was where during the time I was writing about.
And then I found this map. It was a fold out map of Paris, current as of about 1830. Someone had owned this map around that time, and it had been preserved to now. Streets, an idea of the sizes of the buildings. Indispensable.