The Rope Trick spell specifies
Holding one end of a 60-foot or shorter rope causes the other end to rise up until the rope is fully perpendicular to the ground. At the high end, a portal opens to an extradimensional space into which eight medium or smaller creatures can fit by climbing up the rope. The rope can also be dragged up into the space to hide the entrance and the portal itself is invisible.
Spells and attacks are unable to enter or exit the extradimensional space, but those within can see out of it as through a 3 by 5 foot window centered over the high end of the rope.
If everything inside the extradimensional space has not exited beforehand, it will fall out when the spell ends.
Our group has been playing under the assumption that the window is positioned vertical relative to the ground plane, because that's the way most windows we see are positioned. This would mean that you climb into the hole as if on top of a cliff edge at the end of the rope and you then have a view of the world as if you'd be looking out of any normal building window.
However, this seems to be in contradiction with popular depictions on the internet.
The difference would be surprisingly relevant to some standard strategies we have been employing.
How is the Rope Trick portal positioned relative to the ground plane/gravity/the rope?