The final section of the Fossil Creek Trail opened Monday, completing the "missing link" in the Fort Collins trail system.

The $4.5 million addition to the paved trail extends from College Avenue to Shields Street and Cathy Fromme Prairie Natural Area.

The completion of the final 1.7-mile section of the trail connects the east and west sides of Fort Collins and expands the trail system to more than 36 miles of paved, multiuse trail, according to the city.

"The final segment of Fossil Creek Trail represents a culmination of more than 20 years of work and partnerships,” said Kurt Friesen, director of city of Fort Collins Park Planning and Development, in a news release. "The trail provides a significant connection between the east and west sides of Fort Collins.”

More:Long View Trail opens to connect Fort Collins and Loveland

A key part of the project is the construction of the underpass beneath the BNSF Railway, city officials said. The city worked in conjunction with several organizations to construct the 14-foot-diameter tunnel below the functioning railroad tracks. The underpass also allows for the Fossil Creek Trail to connect the west side of Fort Collins to College Avenue.

Through Art In Public Places, artist Stephen Shachtman was selected to design and construct the Fossil Creek Sphere, an eight-foot-wide spherical stone, which will be placed along the trail.

The city of Fort Collins hosted a grand-opening celebration and ribbon cutting Monday on the west side of the BNSF Railway tunnel underpass.

More:New tunnel to link major Fort Collins trails

The trail opens just in time for Winter Bike to Work Day, which is Wednesday.

The grand opening marks the second major trail opening in the latter half of 2018. In August, the Long View Trail — a 4.4-mile connection between Sunset Vista Natural Area in Loveland and Cathy Fromme Prairie Natural Area in Fort Collins — opened to recreators.

For more information about the Fossil Creek Trail project, visit fcgov.com/parkplanning/fossil-creek.

Fossil Creek Trail grand opening ceremony

When: 10 a.m. Monday, Dec. 10

Where: On the west side of the BNSF Railway tunnel underpass along the Fossil Creek Trail.

What: The city invites attendees to travel the newly-opened Fossil Creek Trail by foot or bike. Mayor Wade Troxell, councilmember Kristin Stephens and others will also make remarks during the ribbon cutting ceremony.

By the numbers

Project start: 2016

Finished: Winter 2018

Cost: Trail, $4.5 million total; Tunnel, $3 million; Trail, $1.5 million with $1 million provided by Great Outdoors Colorado grant.