The trip from Portland downtown to the Oregon Zoo is accomplished by riding the train (MAX). Board at the MAX Galleria Station at SW 10th and Morrison.
Be sure to purchase and validate your ticket at the ticket kiosk prior to boarding, or your Trimet trolley ticket can be used if the time has not expired. Be sure you are taking a train to Beaverton or Hillsboro. Get off the train at the Washington Park Station, Oregon Zoo station 4 stops from where you get on.
TriMet’s MAX Light Rail train system connects Portland with Gresham, Beaverton, Hillsboro, Portland International Airport and Clackamas. From downtown Portland, the train takes you into the 3-mile-long Robertson Tunnel.
At 260 feet below ground, the MAX’s Washington Park station (at the Oregon Zoo) is the only completely underground station in the MAX system. It is the deepest station in North America and second deepest in the world (after Moscow’s Park Pobedy at 318 ft).
Before leaving the underground station you might want to look around at the inscriptions on the walls. Amongst other decorations you will see a complete core sample showing the layers of earth above you and the time line when these layers where created.
To exit the train station look for the elevators to the Zoo.
In the elevator you can watch the elevation change as you go up.