Tunnel infrastructure just west of Sydney CBD next to the harbour - the Rozelle interchange

https://en.wikipedia.org/wiki/Rozelle_Interchange

Taken from North Queensferry

Lake Point Tower- Chicago. Completed in 1968 at 645 feet, it stood as the tallest residential building in the world.

Instagram: @hyeonj4e

I had an hour to kill before an airport run, so I went poking around Clinton, New Jersey, and turned my attention to the historic Main Street Bridge.

This one is at the Calancasca Bridge, at the entrance of the Calanca valley in South-Eastern Switzerland.

Instagram: @hyeonj4e

Before radio navigation or modern radar, the US Postal Service had to figure out how to keep airmail pilots on course at night. Their solution was the Transcontinental Airway System.

They built a massive visual highway across the country by pouring 50 foot concrete arrows into the ground, painted bright yellow, with a rotating gas beacon on top. I find it incredible that pilots literally had to look down at the physical ground to navigate across the continent. Once better instruments were developed, the towers were largely dismantled, but many of the concrete arrows are still sitting out in remote areas today.

I put together some more context and maps of the original routes here: https://thehistoricalinsights.page/2026/07/giant-concrete-arrows-america-before-gps.html

Instagram: @hyeonj4e

Up until the construction of the first bridge it was always seen to be impossible to fully cross the Gotthard pass, which now is one of the two main ways across the alps!