Inner Planetary Signpost
An arrow on a signpost points down through the earth to a distant city,
the city's name and straight-line distance printed on the side of the arrow.
In the arrow's tail, a widefield eyepiece provides a view of the far-surface
of the planet, as if the Earth were hollow & translucent and you could
peer through an opening in it. Continents and oceans are perceived in accurate
spatial relationship to your location, and the distant city is centered in
the field of view. Companion installations in sister cities?