Weekend Dungeon (article)
Weekend Dungeon is a weekly event that is located in BWT - Military Area across from the Box Exchange NPCs by talking to Traveler. It costs 400gp to buy one ticket to enter, but upon completion of the the "side quest" you get back 280gp. However, you can only do that once in a given day. To enter the dungeon more than once in the same day, when you exit the dungeon you must abort the quest, which means you won't receive the completion reward.