OK, I'll tell you my Port Arthur tales.
For those that don't know, Tasmania, then Van Diemen's Land, was originally settled by the British as part of the Australian penal colony. Shiploads of convicts were shipped out to Australia, then allocated to free settlers as indentured servants until their time was up.
Recidivist convicts, those that reoffended while transported, were sent to prison where conditions were much harder. The original recidivist settlement in Tasmania was at Sarah Island, over on the west coast. After it was disbanded, the prison at Port Arthur was established.
Conditions here were very bad. The prisoners had to build their own prison, and there were murders, illness and insanity.
Now, 200 years later, much of the Port Arthur settlement still stands. It has, for many years, been rumoured to be haunted. GHI even did an episode here a couple of years back. http://www.youtube.com/watch?v=PJkXECwah8s
Port Arthur gained even more notoriety some years ago when there was a mass shooting there, and 35 people lost their lives. This has cast a pall over the locals there to this day, many of the dead being their friends or family who worked at the site.
Now, I can't vouch for the GHI folk, but I do know what has happened to me and others while at the site.
The site runs multiple nightly ghost tours, and the occasional actual ghost hunt, which I haven't done yet. I've been on the ghost tour twice.
The first time, we (large group) were standing outside the Surgeon's house. In the cellar, he used to conduct autopsies and dissections on prisoners who had died. The slab is still there. Before we went down the stairs, I could smell a very nasty smell - sort of chemical mixed with rotten meat. Several other people could smell it as well. After we went downstairs, the tour guide mentioned that the activity there was normally olfactory - people with medical backgrounds could smell the formaldehyde the surgeon had used - they even had people complaining about them using dangerous chemicals as props. They don't use any props at all. Now, the strange thing here is that all of us that smelled the nasty smell were nurses or ex-nurses. I worked in OR for over 20 years, and used formaldehyde every day, but I'm one of the fairly large percentage that can't smell it, so I had no idea what it smelled like. Well, I do now!
On another occasion, during a daytime visit, Housemate went up the stairs to the chapel in the Separate Prison (which is a very unpleasant place to be after dark, and not nice during the daylight either!) I was down at the base of the steps. She tells me she was nudged from behind, and thought it was me pranking her. So she turned around, to see me miles away from her. I didn't see anyone near her either.
For me, the worst place at the site is the little wooden church, which has no paranormal activity attached to it at all. As soon as I walked in, I felt like I had to leave, now!! And whatever was there wasn't interested in visitors.
The whole site has an atmosphere of being watched.
There is a wall of photos taken at the site near the front entrance - some of them are quite freaky. I've taken many orb shots there, but the staff say they're so common they don't even bother with them any more.