You can’t miss the latest addition to SAM’s Olympic Sculpture Park, and that’s very much the point. When local collector Barney Ebsworth offered the Seattle Art Museum a colossal female head by Catalan sculptor Jaume Plensa, SAM jumped at the chance.

The park was literally designed around Alexander Calder’s soaring steel “Eagle,” and up until now no other single sculpture has been able to match its iconic and skyline-dominating presence. Now comes the Plensa: 46-foot-tall, gleaming white (thanks to a liberal coating of marble dust), and quietly pensive, it stands at the water’s edge like a sentinel, a new landmark for both ships at sea and the odd, perplexed tourist, madly searching a guidebook for the meaning of this enigmatic new wonder.

Neither the title (“Echo,” in a nod to Greek mythology), nor the pose (meditative, eyes closed), nor the odd, highly original vertical distortion to which the head has been subjected, help us quite sort out what drama this appealing and slightly disturbing creature is meant to be enacting.

Up until now, monumental heads were reserved for gods and emperors; perhaps Plensa sees “Echo” as a sort of Spanish Buddha, made even more unworldly by her computer-generated stretching, which gives the impression of an apparition in progress.

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The downside? There isn’t a single trace of an artist’s hand in the giant nymphet’s molded fiberglass surface, arbitrarily subdivided by shallow grooves.

Machine-made, on the other hand, is the perfect look for Ginny Ruffner’s delightful and fully functional park bench, “Mary’s Invitation — A Place to Regard Beauty,” also new to the lineup this summer. The work, conceived as a memorial to park visionary Mary Shirley, is an inspired bit of Art Nouveau whimsy, a silvery gray ribbon that suggests both motion and music, while providing visitors with a front-row seat for the park’s signature view of the Calder and Puget Sound.

Seattle artist Ruffner, whose early work in glass has blossomed into a career equally noted for complex, floral, bejeweled and twisting multimedia sculptures, has created a form with the lyrical energy of her signature work, but stronger for being stripped down and streamlined, reduced to its fundamental energy and sensuality.

There is only incidental visual appeal to the other new piece, a summer-season sound installation by renowned Seattle artist/composer Trimpin, consisting of three sets of steel headphones painted to match the Calder nearby. The work, “You Are Hear,” juxtaposes ambient and engineered sounds, the better to make us conscious of our audio surroundings — as a consequence, it’s as conceptually subtle as the Ruffner and Plensa are visually potent.

I’m not sure that quiet and contemplative are a good match for a site with as many distractions and attractions as the park, and musical in the conventional sense the piece is not, toy-piano soundtrack notwithstanding. My favorite elements of the work are Trimpin’s low-tech inputs, visible just over a fence: a huge rotating rain stick piped into one set of headphones, a huge funnel facing Elliott Avenue collecting sound for another.

Sculpture parks are by their nature eclectic, mixing and matching works of widely differing scale and style. Seattle’s park, a triumph of geoengineering and landscape design, is also a challenge to curate. Going forward, SAM would be wise to go light on the midcentury modern, heavy on the “Wow.”

Gary Faigin is an artist, author, critic and co-founder/artistic director of the Gage Academy of Art.