Rake's Swallet
Many things in the world are elusive, actively resistant to elucidation and understanding; none are as frustrating as those whose study is simply and endlessly fruitless.

Disguised as an army depot, a surplus store for damaged or defunct military equipment awaiting decommissioning, Baker Point was carefully named to be innocuous. Anonymously unremarkable, so bland as to not to draw unwanted or unwarranted attention when referenced in the inevitable and inexorable reams of memos, reports, records and ledgers that governmental bureaucracy seemingly exists to generate, it is actually the site of one of the most constant and consistent esoteric phenomena that has ever been discovered. Referred to as Rake’s Swallet in its limited official mentions (and less neutrally by those whose scientific inquiries it has thwarted) in spite of its unchanging and stable nature, very little definitive information has been confirmed regarding its nature or origins.
At first sight Rake’s Swallet is almost so outlandish, so alien to our perception, that the eye might glance off it. Next is the sensation that it is some kind of optical illusion, perhaps a projection onto glass, because alternative is the existence of a perfectly circular void; as if the world were a static image with a section simply cut out of it. Most see this absence as a white space, with some suggesting that it shades to very light greys, but the best evidence suggests that it neither reflects nor absorbs light anywhere on the visible spectrum. It is, quite literally, a space in which nothing exists at all, and what we see are our brains’ best efforts to comprehend an absence of stimuli. More troubling again is that the Swallet has no physical depth, becoming entirely invisible when viewed from what might traditionally be considered “side on”.
Discovered in Colorado in December 1882 CE while the area was being surveyed for damage and topographical changes resulting from a massive earthquake the previous month, the land around Rake’s Swallet was quietly claimed by the federal government. Such secrecy might have been warranted if it had proven inert - a headache-inducing illusion - but it was quickly discovered to be something vastly more complex and, potentially, dangerous. The earliest interrogations of its nature were laughably artless, an abundance of instinctual caution leading to many thrown stones, but this reticence was immediately borne out: the Swallet is a portal, a one-way door to parts that remain unknown and are perhaps unknowable, and anything that passed its threshold was irretrievably and irrevocably lost.
Over the next few months, a small but secure facility was built around it, with the central chamber that housed Rake’s Swallet off-limits to most of those stationed there. Experimentation began in earnest, and it was found that once part of an object had crossed into the space occupied (or overwritten) by Rake’s Swallet it could not be withdrawn; instead, being pulled gently through. While it is not known whether the force that compels this continued motion is intrinsic to the portal itself or a result of conditions or interventions on the other side, the mere fact of it meant that notions of sending through a tethered human subject were quickly nixed. A few dogs were sent through, with the hopes that they might be able to return of their own volition, but none ever re-emerged.
A few telescopes were passed into the Swallet, but those who looked through the eyepieces before they were swallowed up only reported optical properties similar to what was observable from outside the portal. Similar frustrations met every subsequent advance in remote surveillance, with wired signals either distorted or disrupted to the point of uselessness, and over the following decades the only slight advances in our understanding of Rake’s Swallet are limited to its terrestrial presence. It was, for instance, originally thought to be moving (albeit at a pace of fractions of a millimetre per year) but has latterly been determined that its position is, relative to the centre of the earth, absolute; it is the drift of tectonic plates that is moving the Baker Point facility around it.
More recently it was discovered that Rake’s Swallet is the locus of a weak electromagnetic field that, while almost imperceptible to the human senses, nonetheless acts as a barrier to prevent the transfer of incidental particles and particulates (namely air and dust) from passing through. The resistance to the passage of larger objects, or to gases under targeted and deliberate pressure, is negligible; a stream of air directed at it will pass through the portal with little appreciable hindrance. Other than this though, it appears that Rake’s Swallet has little to no interaction with the physical world; even a true void has qualities that cannot be mapped onto it, and it lacks any of measurable properties of matter or - inasmuch as it can be determined at all - of energy.
Whilst the Swallet itself has always generally been assumed to be a portal, there was briefly some consideration that actually annihilated everything that came into contact with it. This theory was largely abandoned when controlled experimentation confirmed that there were no remnant traces of even the most basic constituent materials from the things that crosses its threshold. To summarise; if Rake’s Swallet is destroying things, it is doing so in a way that circumvents - or, more worryingly, violates - the thermodynamic law of conservation of energy. Less than eager to have a fundamental tenet of physics undermined so utterly, most have returned to their prior assumptions about its nature - though there was a noticeable decline in the enthusiasm of those pushing for an expedition through the portal.
There was a minor internal scandal in the 1920s when it was realised that the staff left in place to monitor Rake’s Swallet had begun to use it as a convenient means of disposing of litter (chiefly the aforementioned memos and various other edicts that pertained to Baker Point but were not, in themselves, overly pertinent to the day-to-day function of the facility). The staff numbers at Baker Point fluctuate in accordance with the relative balance between scientific curiosity, militaristic paranoia and fiduciary restraint of whichever functionary oversees the department in charge of Baker Point at any given time. Nonetheless, it is now overseen by at least two people, neither of whom can access the chamber alone for fear that someone might succumb to an impulsive urge to step through the portal.
Aside from during occasional and irregular flurries of activity - typically when some emerging technology could conceivably offer some new insight into either the makeup of Rake’s Swallet itself or the location of its corresponding exit - Baker Point is staffed by whatever the minimum necessary contingent of supervision is determined to be. It remains wholly inscrutable, with the most fervent investigators and intensive study yielding so little meaningful information that it is likely in more danger of being forgotten than ending up as the focus of renewed interest. Some have even proposed that the chamber itself be sealed up, with enough earth and rocks moved around it to construct a small artificial hill and bury Baker Point completely: Out of sight and out of mind.