We had a lovely bike-ride to Spooners Tunnel and back - a 22 km round trip. It was uphill most of the way, so a very cruisy ride back. Spooners Tunnel is part of an old railway line and at 1.35 km long, is the longest disused railway tunnel in the country. It was opened in 1893 and is all concrete lined. Inside was very dark and a refreshing cool temperature on a hot day.
Great info as well.