I saw this video of a large LEGO train station and I liked the arch in there:

The use of curved train tracked is very neat. However it makes for a big build and I wanted to use something smaller: hence my design, which uses Technic beams.

Here are some more details while I explore the design of it.

The base of the arch:

Base of the arch.

Inside of the panels that line that arch:

Inside of a panel.

And the outside:

Outside of a panel.