Practical information : Take a break South Korea
Timetable
Cafés are open all day and until late at night (10pm-midnight), especially the big chains (Starbucks, Caffé Bene, A Twosome Place, Ediya, Angel-in-us...).
As for bars, they start their service around 5pm-6pm and finish late, around 3am-4am. The same applies to hof (beer and soju restaurants), although they generally close a little earlier.
These establishments rarely have closing days, except sometimes for the smaller ones on national holidays.
Budget & Tips
A single americano or espresso costs around 2,500-4,000 won. That's about the same as in Europe. As for beers and cocktails in bars, the prices are the same as ours. Korean beers (Cass, Hite, Kloud...) are less expensive than those from Europe.
If you decide to drink soju in a hof, the bottle costs around 4,000 won, which is a good deal because it doesn't take much to make you happy. On the other hand, you almost always have to order something to nibble on at the same time (it sponges up!).
Age restrictions
Some cafés, though still quite rare, refuse entry to children in order to preserve calm in their establishment. Fortunately, however, this policy is no longer the exception.
All alcohol-focused places refuse entry to minors (i.e. 19 years old in South Korea). And they systematically ask for proof of identity. They're very particular about this. If, in a group of young adults, only one can't show ID, the whole group won't be served alcohol.
What's very local
Cafés are sacred places here, with dozens of franchises to be found everywhere. For work, family, friends, after dinner... Koreans always gather there to sip a drink and eat a slice of cake. And these cafés have a little special feature that we don't know about: when you place your order, you'll be given a little box that will vibrate and/or light up when your order is ready. At that point, you'll have to collect it from the counter.
When it comes to having a drink, the obvious choice for Koreans is soju, the famous little green bottle that is the number 1 alcohol here. In restaurants and drinking establishments, this rice liquor is everywhere. You can't leave Korea without at least one shot.
Smokers
Smoking is generally prohibited in cafés, bars and pubs. Even if there's a terrace, smoking is prohibited. If you don't comply, you risk a fine that could ruin your stay. Nonetheless, some shops offer customers a small room reminiscent of airport smoking lounges.
Even on the street, it's complicated for smokers. Koreans often hide in small streets or use small structures dedicated to smokers (in Seoul in particular).