The world’s largest-diameter tunnel boring machine will arrive in Seattle next year, but people can get an idea of how it works now.

A 10-foot-long, motorized replica of the machine is on display now at Milepost 31, an information center that highlights the people and projects that shaped Pioneer Square and provides an inside look at the SR 99 Tunnel Project.

About 35 times smaller than the real thing, the model offers an up-close look at the inner workings of the five-story machine that will dig the SR 99 tunnel. The push-button display allows visitors to control some of the model’s parts, demonstrating how the real machine will work as it bores up to 200 feet beneath downtown Seattle.

Milepost 31 is located at 211 First Ave. S. The display is open from 11 a.m. and 5 p.m. Tuesdays through Saturdays. Admission is free.

More information is available at www.milepost31.org.