[1] The blue-gray glass, late-modernist buildings are bounded by Mission, Fremont, and Beale Streets, and the north end of the Salesforce Transit Center site.

The tower's design was marketed as resembling a translucent crystal, and was, until accompanied by much larger adjacent buildings, a landmark for the Transbay Redevelopment and the southern skyline of San Francisco.

According to Modern Luxury, a proposed 52-story skyscraper at nearby 80 Natoma by developer Jack Myers which would also have a similar cast in place concrete construction, was rejected by the city's Department of Building Inspections (DBI) after an outside peer review.

[10][27] Treadwell & Rollo's geotechnical design for the foundation of the main tower consists of a concrete slab built on 60-to-90-foot deep (18 to 27 m) concrete friction piles through the fill and young bay mud, and embedded into dense Colma sand (sand deposited during the last ice age 12,000–100,000 years ago and the penultimate layer before bedrock).

A number of other buildings in 301 Mission Street's area have used similar systems, although due to varying earth conditions, others have pushed piles directly into the bedrock 200 feet (61 m) below.

[30] The sinking problem had reportedly started before TTC construction even broke ground,[29] and TJPA asserted the building had already settled 10 inches (25 cm), well past the original maximum vertical settling prediction of 5.5 inches (14 cm) in 20 years, by the time TJPA began removing the timber piles under the prior Transbay Terminal in 2011.

[30][23] Another group of tenants who disagree with the homeowners association, led by resident and patent litigator Jerry Dodson, is suing Millennium Partners, the City of San Francisco, and the TJPA.

Some experts have prognosticated that the cost to fix the tilt could exceed the liability insurance held by Millennium Partners and the building's various construction vendors.

[8] In March 2017, the homeowners association filed suit against Millennium Partners, Webcor, Handel Architects, Treadwell & Rollo, DeSimone Consulting Engineers, Arup, and Transbay Joint Powers Authority.

The glass used in the building's windows and façade is rated to withstand hurricane-force winds, leading to concern that the crack was a symptom of a much larger structural failure.

Again in March 2023, the San Francisco Fire Department,[41] as well as numerous first-hand witnesses, reported panes of glass falling from the tower during a windstorm.

No injuries were reported.On December 4, 2018, Ronald Hamburger, the senior principal engineer at Simpson Gumpertz & Heger, revealed in a press release a final resolution to the Millennium Tower's tilting and sinking problem by underpinning the building.

The building's tilting problem came under renewed scrutiny following the deadly collapse of Champlain Towers South in Surfside, Florida, in June 2021.

[46] The repair project was halted in August 2021 after monitoring indicated that the building had unexpectedly sunk an additional inch on the Fremont Street side after 39 of the 52 piles were installed.

This gap does not pose a structural safety hazard and is unlikely to worsen during repair work, but reversing the shift would allow the reopening of one of the parking garage elevators.

The revised plan relies on just 18 piles, instead of the original 52, to anchor the high-rise to bedrock on the two sides where it leans and tilts the most, on Mission and Fremont streets.