This character is a Other Symbol and is commonly used, that is, in no specific script. The character is also known as skyline and city.
The glyph is not a composition. It has no designated width in East Asian texts. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. U+1F3D9 offers a line break opportunity at its position, except in some numeric contexts.
The CLDR project calls this character “cityscape” for use in screen reading software. It assigns these additional labels, e.g. for search in emoji pickers: city.
This character is designated as an emoji. It will be rendered as monochrome character on conforming platforms. To enable colorful emoji display, you can combine it with Variation Selector-16: 🏙️ See the Emojipedia for more details on this character’s emoji properties.
The Wikipedia has the following information about this codepoint:
In the visual arts, a cityscape (urban landscape) is an artistic representation, such as a painting, drawing, print or photograph, of the physical aspects of a city or urban area. It is the urban equivalent of a landscape. Townscape is roughly synonymous with cityscape, though it implies the same difference in urban size and density (and even modernity) implicit in the difference between the words city and town. In urban design the terms refer to the configuration of built forms and interstitial space.