Good Morning Rachael,
This reminds me of something I was reading last week - the excavation of the early 17th century glass-making site at Glasshouse, Shinrone in County Offaly, Ireland, last week (see Post-Medieval Archaeology 48(1), 45-89). This is relevant honest!
The furnace seems to have survived as a garden feature for the country house, of 18th century date, known as Glass House. The furnace retained a blue-glazed interior from the glass production so a bit of a landscape feature both for its inside and out.
The other thing it reminds me of is the likes of grottoes where shells, and/or other follies where slag from metal production, have been used as a construction material for also for it's novelty and interest to visitors.
I don't know if those are of interest and/or use for comparisons. Answering your question in light of the above - perhaps something of a structure, if not the ha-ha itself, rather than just a building?,
Keith
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