The European market has been a major part of Amazon’s international business, with Germany and the UK accounting for more than 17% of its total sales last year.

Part of its success has to do with Amazon’s rapid distribution expansion in Europe, as this map from Citi Research shows. Since 2010, Amazon has significantly expanded its warehouse presence in Europe, now reaching countries as far as Romania and Turkey.

According to Citi, Amazon’s investments in Europe’s logistics and delivery infrastructure highlights the company’s focus on growing its same day (Prime) and 2-hour (Prime Now) delivery services there. Prime Now is now available in 9 UK cities and 6 European cities, Citi said.

Amazon delivers to over 50 countries in Europe and has made its Fulfillment by Amazon (FBA) delivery eligible in 26 countries. In aggregate, Citi estimates Amazon has grown its global fulfillment property footprint by over six times since 2010.

Europe is Amazon’s largest overseas market, and Germany and the UK — the company’s two biggest countries after the U.S. — generated more than $23 billion in revenue last year. The company has also announced an investment of $550 million in Italy last year, and plans to open 1,300 new warehouses in the region.

Still, Amazon’s international business only accounts for roughly 30% of its business. In order to boost the growth, Amazon has pledged to invest $5 billion in India and recently bought Souq.com to go after the Middle East.