Eyecatcher in landscape

An eyecatcher is something artificial that has been placed in the landscape as a focal point to "catch the eye" or gain a viewer's attention. It is used to decorate or ornament landscapes for aesthetic reasons, and are typically found in gardens, parks and the grounds of stately homes. Many of these can be found in various forms.

Devices or objects

These can be anything but typically they tend to be

boulders

rockery

trees

Or on a grander scale they can be structures such as a

bridge over a river, a stream or lake as an ornamental feature

conservatory - glasshouses, orangeries, vineries

exedra

folly

gloriettes

grottoes

shell grottos

mausoleums

monopteros

monuments (whether they commemorate anything or just for decoration)

nymphaea

pavilions

reflecting pools

shooting/hunting lodge

summer houses

temples (ornamental or not, as they may sometimes have more than aesthetic use)

Sourced from Wikipedia