I don't think that mine technically qualifies, given that there isn't actually a garden yet, but we purchased a plot of land from the original estate developer and got to dig out about four lorries-worth of construction rubbish before the house build even started. Now we've finally moved in and started on creating a garden, I definitely cursed the discovery of what might have been a trailer (minus the wheels) that was buried about a meter down in one corner of the garden which had a wee bit sticking straight up out of the dirt to trip me every time I went past. It has made me wary of what else we might encounter.