So I have a habit of visiting a fair deal of Nordic prehistoric sites, partially due to the areas often providing good hiking grounds and beautiful naturescapes. Over the years, I have grown to notice that such places tend to sit within a specific bubble of atmosphere incomparable to the surroundings. This may be a tad challenging for someone who has never experienced it themselves to grasp, yet the universal feeling of such a site is almost always the same. For one, something appears to study or stare at the visitor from a distance, sometimes causing them to spin around and only face the quiet trees. In some places, the unidentified presence may appear oppressive, even hostile, and in others it's merely a quiet, sometimes even a becalming effect in the background. Secondly, one may receive illogical chills or even feel that the temperature drops in certain spots, for instance just inside a ring of stones. Other oddments may include an unnatural hush in a previously lively stretch of woods, or a certain sensation of timelessness, as if the claw of civilization had deliberately been thwacked away. The last may well be entirely subjective, however.
This peculiarity applies mainly to barrows, living habitats, and some sacrificial stones from the Nordic Iron Age (500BC-1100AD) or Bronze Age back towards the Neolithic eras (500BC or older). I've included a few pictures.
Perused Hovgården (please see the included Wikipedia links for more comprehensive descriptions of the places, should they sound entirely unfamiliar) earlier this year, and parts of the associated Birka/Björkö island sometime earlier. Both harbored a markedly sinister ambiance, Björkö only around the massive burial mound area behind the old hill fort, Hovgården almost throughout, particularly around a disturbed barrow in the very middle. This is a teeming tourist trap during summertime, but on an April midday housed merely a few ravens cawing in the background. Maybe Huginn and Muninn desired to chase the lone Finnish bugger away.
In another thread, I told about a fellow histrenactor from Poland with similar experiences in relation to Björkö. She began narrating on her own how she'd walked over the turf-covered cairns and felt as if multiple invisible gazes had followed her every step. Ancient kingsbarrows stretching towards the left. The church is built directly upon a pagan temple.
A view from the top of the fourth or fifth mound. The disturbed area right around the clump of bushes felt particularly haunted.
One more image in my runestones thread.
Björkö grave grounds. Thunder was rolling in the background. Every single one of those small elevations stretching towards the horizon is a burial mound.
Sammallahdenmäki, a megalithic cult area from the older Bronze Age, is probably the creepiest example I've come across in Finland. It's slightly difficult to access if you don't own a car: you may have to ride two or more long-distance buses to first arrive in the village of Lappi, then walk about 6km northwards before you can reach a sandy road leading to the woodland area the size of a few square kilometers. In spite of its Unesco World Heritage Site status, the place's thoroughly free and open-access all year round. If one wishes to enjoy silence and inspect the stone constructions at their leisure without hordes of tourists blocking the view, the best visiting time is late autumn before the accumulation of possibly tens of centimeters of snow, and when you may not necessarily bump into a single two-legged being on the forest paths. At that time of the year the sun does not bother to lift its lazy bum much above the treeline, however, so if clouds cover the skies, it will be quite gloomy in the woods even during high noon. Complete darkness may descend around 4pm.
I've travelled there four times now, and on every occasion the otherwordly sensations have crept in around the first long cairn called Kirkonlaattia ('Church floor'; the name derives itself from a local folk legend about a contest between giants and christians over the building of a church. According to it, the giants were driven away by the tolling of a bell the christians had erected as the first item of their project, and thus only a floor remained of the giantish fabrication.). Last year I took a friend there who had never before visited the site. After a while, she began peeking over her shoulder at random intervals, appearing somewhat uncomfortable. At one point--and before I had remarked upon the atmosphere--by a dug-up cairn, she told outright that she felt something menacing staring at her.
Kirkonlaattia
Other cairns:
zorm.deviantart.com/art/Lappi-Barrows-III-47095014
A visible stone coffin
Crude stone altar:
Huilu longbarrow:
zorm.deviantart.com/art/Sammallahdenmaki-I-51443860
Overall, I've met quite a few people who have either agreed or began talking on their own about these sensations in connection to various prehistoric sites (not necessarily Sammallahdenmäki).
I'd be interested to hear if anyone else here shares similar experiences. If you guys are interested, I'll post photos and descriptions of other relevant places. The only area with no known prehistoric landmarks and yet sporting the same uncanny atmosphere was a little park called Hellisgerði in Hafnarfjörður, Iceland. My friend concurred about the certain "Sammallahdenmäki-feeling", which has become a mundane term to address this phenomenon, after wandering amidst the lava formations. Locals tell it's inhabited by huldufólk.
You'll have to remedy your lack of Barrow-downs experiences by traveling to Scandinavia on your next trip abroad. 
