In my working career as a geologist, we were forever poring over old maps when looking for previous uses of an industrial site up for redevelopment. It's difficult to know what contaminants to test for if you don't know the previous uses.
I spent hours poring over those old maps, absolutely fascinating what you can find.
I look at old boreholes stuff on the BGS website from time time, for work. One time I was trying to find out what was under the ground near Brighton and clicked on a borehole near Woodingdean. The scanned documents showed a well 390m deep, which further
time wasting during working hours frantic research showed to be the deepest hand dug well in the UK. There's a letter included, dated 1934, on Volks Electric Railway headed notepaper, signed by Magnus Volk, recounting how he watched it being dug aged 9 or 10. He was 83 when he wrote the letter.