The draw for the round of 16 of the Champions League took place in Nyon, Switzerland on Thursday, and some enticing ties await in the first knock-out stage.Primera Division champions Real Madrid have been paired with Manchester United as Cristiano Ronaldo returns to Old Trafford. Furthermore, 2011 winners Barcelona will have to deal with Italian giants AC Milan in what promises to be yet another mouthwatering tie.Last season's finalists Bayern Munich take on Arsene Wenger's Arsenal as they aim to make it to their third final in five years' time.Serie A powerhouse Juventus will have to deal with Celtic in the first knock-out stage, while Schalke meet Turkish giants Galatasaray.Group winners will be away in the first legs on 12-13 and 19-20 February and at home in the return matches on 5-6 and 12-13 March.The draw for the quarter-finals will be held on March 15, and the tournament concludes at Wembley Stadium on May 25. Champions League round of 16 draw: Galatasaray v FC Schalke Celtic v Juventus Arsenal v Bayern Munich Shakthar Donetsk v Borussia Dortmund AC Milan v Barcelona Real Madrid v Manchester United Valencia v Paris Saint-Germain FC Porto v Malaga