Longest of three tunnels on Sparta-Elroy trail is almost a mile long. In summer there's enough people around that you have to walk your bike through all of them, but they certainly add some character to the trip - bring a light anyway for walking through. Last time I went through last summer I remember the trail being in pretty good shape, but as always be aware of recent rains that may damage the surface. Crushed limestone on both trails, and yes, about 55 miles each way. Last summer I had a funny experience - the lock on the bathroom in the bike shop at the Sparta end of the trail broke while I was trying to leave. The bike shop staff ended up having to take out the knob, then pass some tools through the hole in the door for me to take the hinges off from inside. I imagine it's been fixed now, but be careful...