At long last, the Toronto-York Spadina Subway Extension is open for business – and business is booming (or would have been, if the entire subway line weren't free to ride yesterday).

... Got my souvenir #TTC #TYSSE Line 1 Extension public opening day free all day today transfer !!! ... 🤣 pic.twitter.com/6of5UKETms

— Mike DeToma (@mikedeto) December 17, 2017

Thousands of people flocked to the brand new portion of Line 1 on Sunday for a first look at Toronto's most significant subway expansion in nearly 40 years.

In 1966 my father took me to the opening of the Bloor subway opening that he worked on; In 2017 I brought him to the opening of the #TYSSE pic.twitter.com/PKXffYo1RF

— Joe Mihevc (@joemihevc) December 15, 2017

The additional 8.6 kilometres of subway service starts at Sheppard West station (formerly Downsview) and runs all the way up to Vaughan Metropolitan Centre.

People were excited to ride through the freshly-built (and much cleaner) subway tunnels, but much of hype online this weekend revolved around our six, brand new, state-of-the-art transit stations.

Overheard often today while riding between stations: “I can’t believe how clean these tunnels are!” #ttc #tysse

— Jamie Bradburn (@jbcurio) December 17, 2017

York University station was one of the most popular destinations during yesterday's launch event, as many expected it would be.

"York U station attracted an audible 'wowwwww' from people next to me," wrote one rider on Twitter. "There's an amphitheatre. This station is a huge deal for York U."

Outside, however, in the main centre of York, the exterior is awesome: pic.twitter.com/4pZbrfn7l9

— Casey Goranson (@SeadogDriftwood) December 17, 2017

Students at York are thrilled by the easier commute between campus and downtown, but this station is also thought to be one of the coolest looking on the entire line.

Visitors, students and city officials were all happy to share photos from the new station on Instagram, Twitter, Snapchat, Facebook and wherever else you can post pictures of cool things.

I think I got a tour of the new @yorkuniversity subway from 20+ on my snapchat! #TheExcitement #TYSSE #YorkU

— Alam Khandwala (@K_Wala) December 17, 2017

Many of the new stations featured live bands playing Christmas music on Sunday.

At Pioneer Station, for instance, commuters were treated to the sounds of steel pan drums as they descended into the platform.

Christmas music on the steel pan drum sounding pretty good. #TYSSE pic.twitter.com/GKZyYfF769

— Nick Westoll (@NWestoll) December 17, 2017

This station is also said to have smelled like vanilla.

4. One more north takes you to PIONEER VILLAGE station, This puts you on the North ebd of @yorkuniversity near the PanAm Stadium and a 10 minute walk to Black Creek Pioneer Village. @BlackCreekNews #TTCline1 #Line1Ext #TTC pic.twitter.com/l0IkgxZKNQ

— Steve Russell (@RussellPhotos) December 17, 2017

Many people were impressed with the new Vaughan Metropolitan Centre station at the end of the line, with its domed ovoid entrance and mirrored ceiling panels.

"This is going to be the most selfied station," remarked one person of VMC on Instagram.

I think the thing most worth going to within 10 mins of VMC might well be the pretty spectacular station building itself! Or is that cheating?

— Joseph Moed (@jomo87) December 17, 2017

Highway 407 Station was a hit with its beautiful glass panels. The colourful glasswork, which projects moving colours all over the station when sun shines through its skylights, was designed by Toronto artist David Pearl and is titled "Sky Ellipse."

Highway 407 Station. #TYSSE #Line1Ext #ttc #topoli #onpoli pic.twitter.com/QZKmS11P6E

— Chris Drew (@chrisjamesdrew) December 17, 2017

Design-wise, people are feeling Finch West Station and its striped, bar code cladding.

Things got a bit hairy, however, when one of the brand new station's escalators broke down on the first day of service.

An escalator is already down in Finch West Station. Winter is cruel.

— Asher Mercer (@urban_asher) December 17, 2017

Downsview Park Station, the first stop on the brand new line, also proved a bit annoying to some TTC riders when a passenger alarm went off, causing a slight delay.

A little bit of a photo tweet storm here, Toronto's 6 new subway stations opened to the public extending Line 1 8.6 kms from Sheppard West to Vaughan.
Here are the new stations, one by one working north from Sheppard West.
1, DOWNSVIEW PARK - located at the top of the park. pic.twitter.com/oKuqIw8IKC

— Steve Russell (@RussellPhotos) December 17, 2017

That said, the station goes pretty deep down into the ground - which will certainly be a good thing when it gets hot outside.

Overall observation from #TYSSE opening, lots of people curious about the extension, everyone friendly and interested in the stations. Wide range of ages as well ,Free #TTC helped greatly.

— Alex Lach (@olo114) December 17, 2017

Overall, Toronto seems pleased and grateful for its new, extended Line 1. It may have taken a while, but it's finally here, and will doubtlessly improve quality of life for many commuters between Vaughan and Toronto.