The Lawson Adit is a horizontal mining tunnel found on the UC Berkeley Campus. It was used in earlier times as an educational demonstration tunnel for the school of Mines, located in the Hearst Mining Building. Tours were given in the mine to campus visitors. Now the mine tunnel is closed, although authorized staff sometimes still use the tunnel because of its location: it crosses the Hayward Fault.
Inside the mine are at least two types of mine construction. The beginning shaft is in the older wood timber frame style, while a small side shaft is reinforced with concrete. Mine car tracks are still there, as well as a mine car some distance into the tunnel. Roots from plants growing on the surface hang from much of the ceiling. At the end of the shaft, it appears that some of the tunnel has collapsed or was intentionally filled in.
The tunnel is located on the east side of Hearst Mining Building, just next to a little red shack labelled "Lawson Addition". The gate is firmed locked. However, in dry times, suitably thin people can slide under the bottom of the gate with no trouble. A piece of cardboard makes the problem a bit less messy, since there it is frequently muddy.
The building information as maintained by Berkeley is as follows:
LAWSON ADIT, 1404A, 2,100 Square Feet
LAWSON SHED, 1404B, 178 Square Feet
Here is a picture of the students entering the mine from around 1918.
Here is a geological article that contains an old map of the mine and here is just the interesting part.
Here is a picture of a UC Berkeley professor inside the mine.
There are two photos of me and a friend
entering the mine and inside the mine.
Here is a map I made when I went in around 1993. (not scanned yet)