Faslane Castle, Shandon Castle, and St Michael's Chapel

Near the site of Faslane Castle sits the ruinous St Michael's Chapel, which has also been thought to date to the Middle Ages.

The early 13th century mormaer Ailín II granted an extensive tract of land lying on the eastern side of the Gare Loch to one of his younger sons, Amhlaíbh.

[3] Than to Faslan the worthy Scottis can pass, Quhar erll Malcom was bidand at defence; Rycht glaid he was off Wallace gud presence.

[4] Faslane Castle makes an appearance in the 15th century epic poem, known as The Wallace, composed by the maker Blind Harry.

According to the 19th-century historian Joseph Irving, in the mid 18th century the ruined Faslane Castle "furnished a shelter to the last representative of a once powerful family"—the last clan chief of the MacAulays of Ardincaple.

He stated that the only remaining trace of the castle was a green mound, which overlooked the junction of two deep glens, between two small rivulets of which the banks were steep.

[3] William Charles Maughan stated that the site of the castle could be distinguished, at the time of his writing, "by a small mound near the murmuring burn which flows into the bay".

[8] Maughan also wrote that at Faslane there stood an oak tree at place called in Scottish Gaelic Cnoch-na-Cullah (English: "knoll of the cock"); and that according to legend, when a cock crowed beneath the branches of the old oak upon the knoll, a member of Clan MacAulay was about to die.

In 1963, the OS visited the site and noted that the chapel and the south wall had been rebuilt (without mortar), to a height of 1.3 metres (4.3 ft).