And the most popular tourist attraction in the capital is...

While Luxembourg's network of underground tunnels known as the Casemates were once used to keep people out of the city, today they serve as the main attraction for bringing them in.

The tunnels, carved out of rock, are more than 1,000 years old yet they continue to fascinate and delight, attracting 87,904 tourists from March 1 to August 31, this year.

According to the Luxembourg City Tourist Office (LCTO), there was even a slight growth in visitor numbers compared with the same period last year (0.94 percent).

Of the two sections of the tunnels open to tourists, the Bock Casemates remain the most popular with nearly 76,000 tourists passing through its creepy corridors.

The figures were published in an intermediary report released by the LCTO listing tourism activity from January 1 to August 31.

During that period, 415,477 tourism queries were handled by office staff with 129,046 tourists making enquiries at the capital's tourism office in Place Guillaume II.

The busiest month for tourism queries was August when 27,595 tourists called in. Meanwhile, the busiest day of the year was August 11, the first day of the Streeta(rt)nimation festival.

Business tourism figures remained constant compared with the same period in 2011, with 10 events organised by the Luxembourg Convention Bureau, translating into 1,147 nights at hotels and a sum of 131,102 euros for the hotel industry.