Look what I found: the Pergola and Hill Garden

I was out jogging and got lost. I carried on and found myself in a clearing with a giant open rooved building, buried in the woods over the road from Hampstead Heath and round the back of Jack Straw's Castle. Signs said the Pergola and hill garden were closed for the day and I immediately felt like breaking in. No-one else around. The entire place was covered in green and inside were herb gardens and columns, walkways that stretched out and vines that clutched round stone. A little magic garden all to myself.

I did some research when I got back. It turns out it's rather old. I was going to paraphrase the information I found, but figured I might as well transcribe some of it in original.

'Construction began in 1905. Central to the project was raising the large gardens of The Hill to the required level. This required an army of workers. There were no mechanical diggers or earth-movers then. Furthermore, a vast amount of material was needed. As chance would have it, the Hampstead extension to the Northern Line was being built at the same time. The contractors urgently needed somewhere to dump the spoil from tunnels being created. Soon thousands of wagon-loads of that spoil were making their way to The Hill, with the astute Lord Leverhulme being paid a nominal fee per wagon for accommodating the material that he happened to need to realise his dream.'

So there you go. I was standing on earth tunnelled from beneath the house I live in.