Sentence:  There is just no way to experience these pieces by looking from the outside, or in photos or on video: the initial view of them from the balcony above the Arcelor gallery is impressively dramatic, yet it's the merest <WSD>pipe-opener</WSD> to what unfolds close up and at floor level. 
Meaning of the word marked with <WSD> tags:  An example that serves as an introduction.