Right looking at that map above, i know what my picture is of.As built (1863) it crossed the Hotel Curve just before making a flat junction with the west bound Met/Circle line - the Midland lines were not yet built at the time, and once they were, only a few years later in 1868, the Maiden Lane curve was reported to be filled in. A sketch of the time:
My picture is of Hotel Curve which is boarded up taken from up/dn moorgate's.
When you walk down york way tunnels,where it splits the first split is the maiden lane curve, which is open at that end,but is so black and has warning's signs of sewerage,and dangerous gases i never found the urge to go down there.
The tunnel carries on from the split and comes out by KX Thameslink,which is york road curve.
Hope i'm right or i'll start get angry