Why was I getting an uncomfortable feeling in an R22 at 3,000 feet? I was thinking through my flying experiences when I remembered a strange sensation while I was a student.

In a Robinson R22, with about 35 hours experience, I was doing a solo flyout to a nearby airfield for a cup of coffee and a look at the weekend traffic.  To get there, I had to cross a MATZ which included some permanent danger areas up to 2,500 feet.  I'd transited this MATZ several times with a call to the tower but on this particular occasion, I couldn't reach anyone.

Being quite inexperienced, I didn't know if it was just unmanned, I had the wrong frequency or something else so I decided, with no particular place to go, to climb to 3,000 feet and go over the top.  One lesson learned is how long it takes to get to 3,000 feet in a Robbo, especially in a climbing spiral :)

Anyone who has been in an R22 will know that the visibility is superb and as I climbed, the views were spectacular.

As I got to 3,000 feet and leveled off, I had this strange sensation.  It felt as if the aircraft was balanced on top of a tall pole and the cabin had shrunk to really small. I felt as if the aircraft might tip off the top of this pole and plunge.  I also found it difficult to believe the 70kts indicated since the apparent speed over the ground was so low which makes sense given that I'd only ever been that high as a passenger.

I really didn't feel comfortable although I wasn't scared, didn't have any anxiety and felt fully in control of myself but I did abandon the plan, got back down to the 1,000 feet I was more used to and completed a couple of circuits at my home field before landing.

What did I experience?  Has anyone else had anything like this?  I guess that it might be a symptom of vertigo but I have never had problems before or, perhaps something weird in my ear canals following the long spiral climb followed by a level out?
Typical height for helicopters is 500-1,500 AGL, and almost all flights are conducted in this regime. 

Below 1,500 AGL the surface is quite close and the ground moves by fairly quickly, so you have a good point of reference. 

At 3,000 AGL, you can feel quite disconnected from the earth and can have a bout of altitude fear. 

When I had to circle up above out of a valley airport in an airplane, with minimum VFR visibility due to smoke, I felt like I had to keep cross-checking my instruments to maintain airspeed and bank angle. It was an uncomfortable feeling, even having had lots of hood time and actual IMC. So its not unusual for unusual flight regimes to have an unsettling effect.

The circling could have also cause some disorientation.  

The most important thing, which you accomplished, is recognizing the signs, not panicking, and you kept flying.