Tunnel (Kirkwood, 1883) in Kirkwood, St. Louis County, MO. Big Bend Rd. W. 2.7 miles from jct with I44 exit 278 in Kirkwood, S. (curves W.) on Barberry Ln. 0.25 miles (to end). Park & follow the trail W. about 400’ to the tunnel. (2-11-07, N38 33.91 W90 26.91) Photos by Jack Schmidt.
Below is the article from the waymarking site.

This tunnel, built in 1883 and located in Kirkwood, MO, was part of the old 438 acre Meramec Highlands Resort area, which was popular from 1895 to the mid 1920’s. The large hotel sat above the tunnel.

Drive past the old RR station off Barberry Lane (near Big Bend and HW 270) and park at the end of the road at the Cul-de-sac. Follow the trail to the old train tunnel. At the top of the tunnel you can find remains of the old hotel and fountain.

Getting to the top can be very slippery and dangerous and there are no obvious trails. You are on you own if you go up on top.

The homes along Ponca Trail were once cottages for the Meramec Highlands, offering a total of 125 rooms. After the area shut down, the tunnel was used for growing mushrooms. 23 year old “Pretty Boy Floyd” was arrested in 1925 for robbing the Meramec Highlands Store and served time in Jefferson City penitentiary. From downtown, Frisco RR ran nine trains daily on weekdays and four on Sundays. Commutation tickets were for 100 rides, good for 90 days and costs $14.75. One round trip ticket was $.50.

Just east of the RR station at Big Bend and 270 (off Marshall Rd.) is Meramec Highlands quarry (now called Dee Kestering Park) that was used to build the RR station, along with some of the homes in the area. Some of the stone for Union Station downtown and the structures for the 1904 Worlds Fair in Forest Park came from this quarry also.