From the little village of Kilchattan Bay at the southern tip of The Isle of Bute a walkway continues south for a mile or so where you can visit the ruin of the 6th Century St. Blanes Chapel. There are Viking gravestones cut with Runes.
On the way across the valley you can see from above the vitrified fortified village of Dunagoil. There is clear evidence of Iron Age habitation. Open to all free.
There are regular buses from Rothesay to Kilchattan Bay.