Not a traditional transit map per se, but a stunningly beautiful technical illustration of the interlinking tubes and tunnels that form the connected Bank-Monument tube station complex in London. Built as separate stations, but linked by escalators in the 1930s (the depiction of which proved a permanent puzzle for H.C. Beck on his Tube Map), the complex is the ninth-busiest London Underground station,

What I love here is that we’re looking at over 100 years of infrastructure development: the original Monument station (first called “Eastcheap” and then “The Monument”) opened in 1884; the “City” end of the Waterloo and City Line in 1898; Bank station (named after the Bank of London) opened in 1900. Over 100 years after the first part of the complex was opened, the deep station for the DLR was completed in 1991.

Compare to a similar cutaway of the Hudson River Tubes from 1909.

Source: Original source unknown, image from skyscrapercity.com forum post