It took me a few moments to realise where the umbrella was in this composition when it came up - my first impression of it was that it was a form of octagonal black stop sign - which slowed the viewing down so as to study it. By definition a portal is a doorway or entrance which is usually imposing and this fits quite well. I like the rest of the photograph also - the cloudscape & the reflection in the water; the textures of the earthen road leading up to the bridge and the lines of the backstop & guardrails.
I would go where this beckons.
I would have liked to grade this higher, I like the concept a lot. The image is just a little too dark for me to focus o the umbrella or really any focal point. Nice concept though.