This club is the best option on Monday nights. They have the Welcome International Students Party. You can get the invitations at Don Quijote and Enforex Schools. All the new and old students love to go there to meet the new people that are coming and also to have loads of fun. It's free with invitation before 1am, otherwise it costs 8 euros with a free drink. It has 2 floors and a terrace. It is right in the heart of Barcelona, just a few steps from Las Ramblas. Check this place and make your Monday night excited. I suggest to go to Gao Negro before, you can have cheap drinks and it is really close to City Hall.