Information from Wikipedia - all sources there.
McCaig's Tower is a prominent folly on the hillside (called Battery Hill) overlooking Oban in Argyll, Scotland.
It is built of Bonawe granite taken from the quarries across Airds Bay, on Loch Etive, from Muckairn, with a circumference of about 200 metres with two-tiers of 94 lancet arches (44 on the bottom and 50 on top).
John Stuart McCaig was his own architect.
The tower was erected between 1897 and his death, aged 78 from Angina Pectoris, on 29 June 1902 at John Square House, Oban, Argyll.
McCaig's intention was to provide a lasting monument to his family, and provide work for the local stonemasons during the winter months.
McCaig was an admirer of Roman and Greek architecture, and had planned for an elaborate structure, based on the Colosseum in Rome.
His plans allowed for a museum and art gallery with a central tower to be incorporated.
Inside the central tower he planned to commission statues of himself, his siblings and their parents.
His death brought an end to construction with only the outer walls completed.
more on wikipedia site, feel free to add more here too.