Marchmont House
... that the 1.3-mile (2.1 km) avenue of trees leading to Marchmont House in Scotland was begun 24 years before the house itself was built, with the planting of 10,000 Dutch elms?
... that the <span about="#mwt11" data-mw='{"parts":[{"template":{"target":{"wt":"convert","href":"./Template:Convert"},"params":{"1":{"wt":"1.3"},"2":{"wt":"mi"},"3":{"wt":"km"},"4":{"wt":"1"},"adj":{"wt":"on"}},"i":0}}]}' id="mwow" typeof="mw:Transclusion">1.3-mile (2.1</span><span about="#mwt11" typeof="mw:Entity"> </span><span about="#mwt11">km)</span> <a href="./Avenue_(landscape)" id="mwpA" rel="mw:WikiLink" title="Avenue (landscape)">avenue</a> of trees leading to <b id="mwpQ"><a href="./Marchmont_House" id="mwpg" rel="mw:WikiLink" title="Marchmont House">Marchmont House</a></b> in <a href="./Scotland" id="mwpw" rel="mw:WikiLink" title="Scotland">Scotland</a> was begun 24 years before the house itself was built, with the planting of 10,000 <a href="./Ulmus_×_hollandica_'Major'" id="mwqA" rel="mw:WikiLink" title="Ulmus × hollandica 'Major'">Dutch elms</a>?