calder gardens: take a first look at herzog & de meuron and piet oudolf's philadelphia oasis

Calder Gardens Opens as a Living Museum in Philadelphia

On September 21st, 2025, Philadelphia will see the opening of Calder Gardens, a new park and museum shaped by Herzog & de Meuron and Piet Oudolf. Rather than presenting a monumental museum, the project frames Alexander Calder’s work within a lush, layered landscape that gradually reveals its structure and galleries as visitors move inward from the city. The project occupies a city rich with the Calder family’s history. Alexander Calder’s grandfather and father both left their mark on Philadelphia, and works by all three generations line the Parkway.

From the Parkway, a long tapered metal wall forms an austere backdrop to the meadowed garden, softening the sound of nearby traffic and leading to a wood-lined entry beneath a folded metal canopy. The architecture remains deliberately understated. A circular disc at the center creates a plaza and conceals the main galleries below ground, while two sunken gardens — one perfectly round, the other irregular — bring daylight into the galleries and offer distinct settings for Calder’s sculpture.

Today, September 15th, designboom visited Calder Gardens ahead of its public opening to experience Piet Oudolf’s meadows in dialogue with Herzog & de Meuron’s architecture in-person — stay tuned for updates!

subdued architecture by herzog & de meuron

Inside, visitors to Philadelphia’s Calder Gardens descend from a modest lobby to a series of Herzog & de Meuron-designed galleries that vary in light and proportion. The ‘Highway Gallery’ offers a view of Calder mobiles from a mezzanine, while the ‘Open Plan Gallery,’ set beneath the central disc, receives natural light and frames views of the Vestige Garden. Smaller spaces such as the Apse and Curve galleries provide intimate settings for works on paper and light-sensitive sculptures. The architects plan each room to encourage a slow, careful encounter with Calder’s art.

Jason Frantzen, senior partner at Herzog & de Meuron, describes the project as ‘both an actual and a conceptual garden,’ designed in close collaboration with the Calder Foundation and the Barnes Foundation to honor Calder’s legacy while creating ‘a space for all Philadelphians and visitors alike to discover Calder’s work again and again.’

lush landscape design by piet oudolf

Piet Oudolf’s 1.8-acre landscape surrounds and threads through the architecture throughout Calder Gardens, transforming a once-overlooked site in Philadelphia into a shifting, four-season meadow. More than 250 plant varieties — grasses, perennials, and woodland species — form a living composition that changes with weather and time. Paths curve through woodlands, perennial meadows, and tall borders, drawing visitors toward the central disc and framing new views at every step.

From the West Woodland Garden’s young oaks to the late-summer prairie grasses that sway near the building’s edge, the landscape designer’s planting encourages a pace that’s slow and contemplative. The sunken Vestige and Sunken gardens, visible from the main galleries, are a living hybrid of art and landscape. As Oudolf notes, ‘Gardens are for everyone.’