A 12km return walk in Brisbane Water National Park to a hand cut sandstone tunnel under the railway, with a pool alongside. Only walk it at low tide.
This is one of my favourite big day walks in Brisbane Water National Park. It follows the Tunnel Fire Trail off Woy Woy Road, drops down to Mullet Creek, and finishes at a hand cut sandstone tunnel that carries the creek right under the Sydney to Newcastle railway line. On a warm, clear day the pool beside it is perfect for a swim, and standing inside the tunnel looking up at the stone arch is quietly astonishing.
The tunnel is a piece of living history. The culvert was built in the 1880s to let Mullet Creek pass beneath the main northern railway, and the ridge above it holds the Woy Woy railway tunnel, which at nearly 1.7km was the longest railway tunnel in Australia when it opened in 1888. You are walking through a Victorian era engineering feat that thousands of people ride straight over every day without ever knowing it is there.
It is a proper 12km return, mostly along fire trail with a steep pinch down to the creek and back up again, so bring plenty of water, sturdy shoes and a sense of adventure.
Warning: Only do this walk at low tide. The tunnel fills as the tide comes in, so check the tide times before you set out and leave yourself plenty of room to get back.
