What is happening at the Mill Avenue Underpass?  

Construction of the first phase is underway at the Mill Avenue underpass as Tempe prepares for the installation of “Sun Garden,” a vibrant public art project. Structural repairs to the underpass retaining walls were completed in the middle of May to ensure they can support the 15 new nature-inspired sculptures designed by Arizona-based artist team, Joseph O’Connell and Creative Machines, Inc. The translucent, colored elements will cast shifting shadows throughout the day and be illuminated at night. 

Phase 1 is close to complete. The sculptural artworks were installed in the summer of 2025. Landscape improvements are anticipated to begin during the fall of 2025 completing this phase of the project by September 2025.

Phase 2 will focus on lighting. City of Tempe and partners are working on an electrical plan, with installation scheduled once the required power is available. When this Phase is complete, the underpass will be a colorful, welcoming landmark for all to enjoy – day and night.

Why is this art piece being installed? 

This project is part of the City’s Refresh Tempe initiative to enhance public spaces and reflects the community’s input and creative spirit.

Over the last several years, the Tempe City Council has been increasing reinvestments in parks, streets, public art and more. This Refresh Tempe initiative aims to add and maintain Tempe amenities and infrastructure in order to improve quality of life for all community members. The project also aligns with the Tempe Arts + Culture Plan, which calls for signature works of public art.

This regionally distinctive project will bring the highly trafficked underpass to life in a dramatic way. For many travelers, this stretch of road serves as a gateway to Downtown Tempe and Arizona State University. Approximately 18,000 vehicles travel the underpass daily in addition to the pedestrian and bike traffic in this corridor, which encompasses Tempe High School and Tempe St. Luke’s Hospital.

Phase 2 is not expected to impact traffic.



What will the art piece look like? 

The art, titled “Sun Garden,” includes nature-inspired sculptural elements that will stretch upward from the existing terraced planters along the west side of the underpass. The sculptures’ translucent material is designed to catch sunlight and project colored shadows along adjacent surfaces, changing throughout the day as the sun rises and sets.

In total, the artwork includes 15 sculptures made from steel and a colored polycarbonate material. The design was inspired by the many gardens in the surrounding neighborhood. After power is added to the site, lighting features will be installed to wash the walls of the underpass in color at night.

How was the art selected? 

A national artist competition was held to select the artist for this significant installation. Arizona-based artist Joseph O’Connell + Creative Machines, Inc. was chosen to design the project, and fabrication is currently underway. Tempe Public Art hosted several public meetings with the surrounding neighborhood and Tempe High School to gather input about the design.

Will supportive landscaping be added to the installment?  

Yes, the space is designed to be fully enhanced with complementary landscaping that beautifies and completes the overall installment. Landscaping will be contingent upon city infrastructure schedules and are expected to be addressed in fall/winter 2025. 

Will the art piece have lighting at night? 

Yes, the piece will be vibrant and highly visible at night once power and infrastructure and power are activated; installation is anticipated to be complete end of 2025 or early 2026.