Learn English – What do you call those high areas that give you a full view of the city

A common term for a place that affords such a view would be a scenic overlook or simply a scenic view:

A scenic overlook, or just an overlook, observation point, lookout, viewing point or vista point is a high place where people can gather to view scenery (often with binoculars), and to photograph it. Scenic overlooks are typically created alongside mountain roads, often as a simple turnouts where motorists can pull over onto pavement, gravel, or grass on the right-of-way. Many are larger, having parking areas, while some (typically on larger highways) are off the road completely.

Here are some signs to such:

An older word, now more restricted to a piece of architecture meant for such purposes, is a belvidere or belvedere.