Tottenham started their summer recruitment drive with the £4million signing of Austria center-back Kevin Wimmer from Cologne.
Tottenham manager Mauricio Pochettino has highlighted defence as one of the areas where his team needs to improve next season and he has moved quickly to sign 22-year-old Wimmer on a five-year deal.
Pochettino gave spells to Vlad Chiriches, Younes Kaboul, Federico Fazio and Eric Dier alongside the near ever-present Jan Vertonghen, but Spurs regularly looked weak at the back last year.
Despite qualifying for the Europa League, Spurs had the joint-fifth worst defensive record in the Barclays Premier League last season, conceding 53 goals in 38 matches.
Wimmer is looking forward to the challenge of breaking into Tottenham's first team.
He told Cologne's website: "Tottenham is a huge chance for me. Nonetheless, it won't be easy saying goodbye to Cologne.
"I experienced wonderful moments here, such as the promotion and the Klassenerhalt (staying up).
"I want to thank the training staff, my team-mates, and all those involved in the club for their extraordinary support.
"FC and its fantastic fans will always remain something special for me."
Cologne general manager Jorg Schmadtke added: "Kevin has improved tremendously during his time here and has developed into an Austrian international player.
"Of course it is with some regret that he will be leaving us, but we understand that he is getting the opportunity to play for one of the biggest traditional clubs in London.
"In our dealings with Tottenham we were able to reach an agreement that all parties were happy with."
Pochettino is expected to add further names to his squad this summer.
The Spurs boss has been linked with players like Danny Ings and Morgan Schneiderlin as he looks to turn Tottenham into serious challengers for Champions League qualification next season.
Chairman Daniel Levy insists he will leave it up to the Argentinian to decide who comes and goes at White Hart Lane this close season.
"As has always been the case the coach always makes the final decision," Levy said in a Facebook Q&A session with fans.
Pochettino gave Harry Kane his maiden run in the Tottenham first team last season and the move paid off handsomely, with the striker scoring 31 goals.
Next term, young striker Alex Pritchard will be given a chance to make his mark on the first team after scoring 12 goals on loan at Sky Bet Championship side Brentford.
"He is in our plans for next season," Pochettino said of the 22-year-old.
"He starts pre-season when he gets back from the (Under-21) Euros and we are looking forward to having him back after a successful loan with Brentford."
Spurs will round off their post-season tour on Saturday when they play Sydney FC.
On Wednesday Tottenham beat a Malaysia XI 2-1 in Kuala Lumpur thanks to a brace from Kane, who was substituted after 57 minutes.
