Question: What structure dates back to 1502 and its 10th laird was a Scottish Politician known for the Montgomery Plot?
Context: Captain Benjamin Moodie (1789 - 1856) was the 10th Laird of Melsetter who led a party of 200 Scottish immigrants to the Cape Colony in 1817, three years before the arrival of the 1820 Settlers.  Benjamin was considered the hero for scots in south africa. The Douglases of Mains are a branch of the Clan Douglas, related to the Lords of Douglas through Archibald I, Lord of Douglas.  The first Laird obtained land through marriage into the Galbraith family, which had been granted land in New Kilpatrick by Maldowen, Earl of Lennox.  The family produced minor nobles in the Scottish court, perhaps the most notable of which was Malcolm Douglas, the 8th Laird, executed for treason in Edinburgh for conspiracy in the Raid of Ruthven.  His second son, Robert Douglas, was made Viscount of Belhaven and is buried in Holyrood Abbey.  The family intermarried in the Glasgow area, having links with the Campbells of Blythswood, with landed families across Scotland (including the Duke of Douglas) and more latterly the United Kingdom.  The title became extinct in the 20th century; the last 33.5 acre of the estate (including the house) was sold to Dunbartonshire county and was subsequently used for the erection of the secondary school, Douglas Academy, in Milngavie prior to the death of the last heir (Lt-Col Archibald Vivian Campbell Douglas) in 1977. Kenneth Mackenzie (died 6 June 1568), was the 10th laird of Kintail and he was nicknamed "Coinneach na Cuirc" in Scottish Gaelic (or “Kenneth of the Whittle”), was a Highland chief, head of the Clan Mackenzie, who flourished in the turbulent Scottish politics of the mid-16th century. Alexander Fraser, 11th Lord Saltoun (1604–1693), was a Scottish peer and the 10th Laird of Philorth. Sir Hugh Montgomery, 1st Viscount Montgomery of the Great Ards (c. 1560 – 15 May 1636) was an aristocrat and a soldier, known as one of the "founding fathers" of the Ulster-Scots along with Sir James Hamilton, 1st Viscount Claneboye.  Montgomery was born in Ayrshire at Broadstone Castle, near Beith.  He was the son of Adam Montgomery, the 5th Laird of Braidstane, by his wife and cousin. Sir James Montgomery, 4th Baronet (or Montgomerie, died 1694) was the tenth laird of Skelmorlie.  He was a Scottish politician known for the Montgomery Plot, a Jacobite scheme to restore King James VII and II to the thrones of Scotland and England. Sir James Campbell (1745–1831) was a Scottish officer of the British Army, and author of "Memoirs of Sir James Campbell of Ardkinglas, written by Himself".  Until 1810 he was known as James Callander.  While not a baronet, as he claimed, he used the title "Sir".  James Callander Campbell was 5th Laird of Craigforth and 15th Laird of Ardkinglas. Casa Fontana-Silvestri is one of the few Renaissance buildings surviving in Milan, Italy.  The main structure dates back to the 12th century, but its current form is due to a thorough modification that were made at the end of the 14th century, in a style that mixes Renaissance and Gothic elements. Archibald Napier, 1st Lord Napier, the 9th Laird Napier of Merchiston (c. 1576 – November, 1645), was a Scottish politician and judge.  In 1627 he was created Lord Napier of Merchiston and Baronet of Nova Scotia. Skelmorlie Castle stands on the eastern shore of the Firth of Clyde, Scotland, at the north-western corner of the county of Ayrshire.  The structure dates from 1502, and was formerly the seat and stronghold of the Montgomery Clan.  The modern village of Skelmorlie lies to the north of the castle.
Answer: Skelmorlie Castle