Opened in 1905, the Gwangjang Market is Korea's oldest daily still running market. It is one of the largest markets in Korea, too. The market specialises in traditional Korean cuisine, which is its biggest draw. There are also some stores selling fabric.
On the market, which got a roof in 2005, but otherwise seems quite unchanged by time, you can fill your belly with some of the market's specials, like the bindaetteok, bibimbap, sundae or a live octopus.
The food is mostly sold from small stalls (which are organized into two lanes) and made on the spot. You can either eat it on one of the benches which can be found all over the market (but are usually occupied, as the market is generally a very busy place). Visiting the market also offers great way to get to know Korean culture closer, as you will get to mingle with the locals, who came in search of a tasty snack, too.
Wikipedia https://en.wikipedia.org/wiki/Gwangjang_Market
Official Website http://www.kwangjangmarket.co.kr/
Phone +82 2 2267 0291
Address 88 Changgyeonggung-ro, Jongno-gu, Seoul, South Korea
Coordinates 37°34'12.598" N 126°59'58.164" E