With around three million day-trippers every year, Heidelberg can boast some of the most impressive visitor statistics in Germany, Europe and probably the world. In some ways this is a shame, because one day really isn't enough. Those who stay just a little longer will discover a host of attractions away from the beaten track and will have more time to soak up the unique atmosphere that sets Heidelberg apart from your average university city. The main attraction for all visitors is, of course, Heidelberg Castle, perched on the slopes of Mount Königstuhl some 70 metres above the Neckar. It's easy to see why, too. Together with the Old Bridge across the river, the castle and its neighbouring buildings are among the most impressive sights anywhere in Germany. Although you can explore the ruins under your own steam, it's well worth joining a guided tour, if only to appreciate the history of this mighty fortress, which has experienced its fair share of ups and downs over 700 years. To get them through these turbulent times, it's likely that the lords of the castle would have made regular use of the royal wine cellar. This is home to the biggest wine barrel in the world. Made from 130 oak trees, it is seven metres wide, over eight metres in length and has a capacity of precisely 221,726 litres. For a time, Elector Karl Theodor employed the Italian court dwarf Perkeo to guard the barrel. Perkeo's name is said to have derived from his fondness for drink. Whenever anyone asked him if he would like another glass of wine, the answer came back "perché no?" – why not?

The castle has also established a reputation for its summer castle theatre festival, first held in 1926 and now one of the best-loved outdoor theatre festivals in southern Germany. From the castle, a path takes you straight down into the old town, which features an important site of remembrance amid its beautiful streets. The permanent exhibition at the Documentation and Cultural Centre for German Sinti and Roma sheds light on the lives and fates of these people and serves as a poignant reminder of the Nazi-era genocide. At the centre of the old town is the market square, where you'll find another of Heidelberg's many beautiful fountains, alongside grand period houses, lots of cafés and even more pretty little shops. Towering above this delightful scene is the famous Church of the Holy Spirit. From here it's just a stone's throw to Kornmarkt, for many Heidelberg's prettiest square. The Madonna from 1718, who is held aloft by angels atop a fountain pillar, was meant to entice Protestants to return to the 'true faith' following the Catholic Revival. Today we can all enjoy the statue, which combined with the castle forms one of Heidelberg's most popular postcard motifs. The next square, Karlsplatz, is also decorated by a fountain, which offers a playful take on the famous humanist and cosmographer Sebastian Münster. That such feats should be honoured reveals much about Heidelberg. Because over the course of the centuries a great many scholars have shaped the intellectual and cultural ideas of this former electoral seat. Georg Wilhelm Friedrich Hegel, Robert Bunsen, Max Weber and Karl Jaspers are just some of the famous names who have studied or taught at the university – the oldest on German soil. Today, around 30,000 students are enrolled there, and although they work hard, it's not uncommon to see them in the numerous cafés and drinking establishments. The best thing is: you too can feel like a student in the welcoming and time-honoured student bars, no matter how old you are!