"spectacular viewpoint" is a correct and usable phrase in written English.
It can be used to describe a breathtaking or impressive view from a certain location. Example: As we reached the top of the mountain, we were met with a spectacular viewpoint of the surrounding valleys and peaks.
We pay $10 to take the seven-mile Pierce Stocking scenic drive – a gentle loop through woodland with spectacular viewpoints over forests and lake.
Below Ross it repeatedly engages in the Forest of Dean plateau in deeply entrenched meanders that provide impressive scenery and spectacular viewpoints, notably at Symonds Yat (an opening or pass).
It's a hilly city and this makes for spectacular viewpoints everywhere.
Having felt an urgent need to photograph every inch of this magical, geologically unique wonderland, we set off on a snowshoe walk to the spectacular Pariah viewpoint a little later than planned.
Alternatively, they might go to Castle Neroche in Somerset, where a stroll out to the viewpoint will offer spectacular views over the Vale of Taunton towards the Quantock Hills and Exmoor.
You may or may not believe, as I do, that the Guggenheim Bilbao is the best building of the last half century: indeed spectacular, differently so from every outer viewpoint, but embracing when you enter, and modulating gracefully from sculptural bravura to fine rectilinear spaces for displaying works of art.
For the most dramatic views, ride the spectacular Flåm Railway all the way from Bergen, or drive the Aurland Mountain Road to the Stegastein viewpoint at 650 meters.
Today, for scenic views, hop over the metal barricade at the main viewpoint for the valley above the parking lot: an overgrown hiking trail slithers around the mountainside, offering ever-more spectacular views of the Iao Needle.
