The main road pretty much ends at the ruins,it is all accessible by bike,from Greyfield inn dock it's a little over a mile ,I believe, mostly hard packed dirt road and trails are easy to ride on,with many nice spots to stop and rest along the way,well worth the effort to explore Dungeness...looking to the south from behind the ruins,across the marsh ,is one of my favorite views on the island. Must have been a true privilege to enjoy it back when it was in its prime...
There are bikes that you can rent. I am not sure about bringing your own There is a dirt road that you could ride the bike on. I would say the ruins are a mile to a mile and a half from the dock. You cannot ride bikes in the dunes. We circled the whole island path. We walked 6 miles. The dunes are a bear to walk.
It's $10 extra roundtrip to bring your own bike and yes you can access the ruins by bicycle. The main road from the ferry dock leads right to the ruins if you go south.
Biking is a great option for interior paths and can help transport camping gear to your camp site too.
Bikes are not allowed on anything other than the road there, and I don't recall there being one that led to the ruins.
The entire path is bike accessible. The hike from the ferry dock depends on where you go. If you hike straight across to the beach it's about a mile and a half. We walked around the perimeter of the lower half of the island to the ruins from the beach then back to the ferry dock. It was about 8 miles.
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