Waiting for them on the platform - red hearts daubed on the windows and red, heart-shaped balloons strewn throughout - Berlin's famous "panorama train," transformed for the night into the "Flirt-Express," the venue for Germany's unusual speed-dating party on the rails.
Upon arrival, women are presented with a single red rose and men with that very German delicacy, a pretzel - maybe not sexy but heart-shaped.
Who says romance is dead? It's the second year running that German train operator Deutsche Bahn has staged the free event. And Berliners were not the only ones enjoying its hospitality.
The "nationwide flirt" took place in 10 German cities on Valentine's Eve, the train operator said, with demand outstripping available seats six-fold.
In the capital, the singles, ranging from late teens to late middle age, are guided straight to the platform bar where, to get the lonely-hearts in the mood, party music blares and sparkling wine fizzes from bottles.
Standing in nervous circles, clutching plastic cups and looking potential partners up and down, the party-goers listen as the Deutsche Bahn moderator runs through the evening's rules.
For Cupid's arrow to strike on the Flirt-Express, it has to be love at first sight. Each encounter is brief: three minutes to chat and size each other up. Women sit in the same seat for the entire trip and the men change places.
When the time is up, it's "all change please" and on to the next candidate. "If you decide you like someone, you write their name down on the 'flirt-list' and you get their contact details next Friday," the moderator explains.
"Go to the toilet now," he advises. "You'll need all the time you can get for flirting!"
And with that final piece of advice, it's all aboard for the non-stop two-and-a-half hour journey - you can't leave if it's going badly – around Berlin's local train network.
Deutsche Bahn is not the first German transport authority to try to give Cupid a helping hand.
For Valentine's Day in 2007, Berlin's city transport authority (BVG) launched what it called an international first - a free online service to give commuters smitten with someone they spotted on a Berlin metro, tram or bus line a chance to try to meet up. And the site, www.bvg.de/augenblicke, is still going strong.
On the ride from Potsdamer Platz, the train trip itself is not the end of the line as flirting continues at a bar in Berlin's trendy Hackescher Markt where, it seems, Cupid's quiver was not completely full.
While two or three intimate couples whisper sweet nothings into each other's ear - or rather shout over the party music, others sit mutely but contentedly with members of the same sex, casting wistful glances around the room. One lone woman struts her stuff on the dance floor, and several other singles sit alone, dispirited.
Opinion amongst participants was similarly split.
"It was a totally positive experience, surprisingly. I've been speed dating before but this was nice because you were side by side and it was a bit more intimate," said 22-year-old Carmen, who did not give her last name. "I met about 12 guys and I put six or seven down on my list," she enthused.
A man - who gave his age as "late 20s" but no name - also found the evening "really cool."
"I wouldn't say I met anyone incredible but it was fun," he said, after putting three names on his flirt-list.
Unfortunately, the love bug did not strike everyone.
"I don't really want to talk about it," said one man sitting glumly on his own nursing a beer.