The Lowell Creek Diversion Tunnel is an oddity worth seeking out. Built in the 1930s to prevent flooding, the tunnel carries Lowell Creek through the mountain and sends it shooting out through a concrete flume directly into Resurrection Bay. You can walk to the outlet, a short hike from the south end of town, where the creek emerges in a powerful cascade visible from the bay.
The inlet side, near Lowell Canyon, is also accessible. A short trail leads to the concrete intake works where the creek disappears into the mountain. It is an impressive piece of engineering in an unexpected setting — the sound of rushing water in a dark tunnel under an Alaskan mountain is memorable. The trail continues up Lowell Canyon past several small waterfalls if you want to extend the walk.