This was a mistake, this travels back in time.
Could it be that Earth's magnetic field has an influence on the direct of time travel.
If this is the case, stepping back into the arch reverses the direct of travel and brings one back to the future.
To travel into the future,
The supportive frame would be a different material from the pyramid and arch. A narrow strip of stairs up the structure, might just be the short stroke at the bottom of the character '舟'.
Saw this as a glyphs somewhere...Where?