The arts-loving Elector Palatine Carl Theodor extended and transformed his ancestors' hunting castle into a luxurious summer residence, a 'mini Versailles' in the Palatinate. Schwetzingen's most striking architectural feature – and the only example in Europe – are the Zirkel: a pair of single-storey, semi-circular buildings added to the palace on either side. The northern section of the Zirkel contains a charming, rococo-style, 500-seat theatre, built for the Elector as a promoter of the arts. This is one of Germany's few 18th-century court theatres to have survived in its original state . It is still the venue for operas during the Schwetzingen Festival. A semi-circle of arbours was added to the Zirkel to form a complete circle and provide a perfect backdrop for glittering events that spill out into the surrounding park. Distinguished architects and landscape designers of the time created a prestigious masterpiece of baroque landscape gardening here. Foremost among them was Nicolas de Pigage, who entered the service of the Elector in 1749. The Frenchman built an orangery, the court theatre and all the park's architectural features. The strictly symmetrical baroque garden with its flowerbeds, geometric clipped hedges, 'outdoor cabinets' and various fountains was also designed by him. Visitors are continually accompanied by the gentle babbling of the streams, cascades and fountains as they stroll around the grounds, which give way to an English-style country park. Even as distinguished a guest as Voltaire, the French writer and philosopher, was impressed by the beauty of Schwetzingen's illusory surroundings. Nearby attractions: the 'Fantastic Road' joins the dots between the prettiest towns and cities in Baden-Württemberg. Schwetzingen Palace is also a stop along the German Castle Route, which links more than 70 castles and historical palaces. Also close by is Speyer Cathedral, Europe's biggest Romanesque church and a UNESCO World Heritage site since 1981.