Dear Christian, thank you for your inquiry. 50 km is quite a generous radius, there will be plenty of available activities, and it will be hard to narrow this down. As you saw, the lake itself offers lots of nature-related activities such as kayaking, canoeing, stand-up paddling, but also hiking and swimming. There are ruins of a castle in Esch-sur-Sûre, about a 5 minute drive away, but also plenty of other castles, the most spectacular of which are Vianden (36 km), Bourscheid (17 km), and the two castles of Beaufort (39 km). A fifty kilometre radius would include Luxembourg City, which is home to a dozen museums ranging from modern art to history. The City also offers a very interesting programme called 'Summer in the City', with plenty of free concerts and performances. Depending on the season you plan on visiting, I recommend you look into it. Many people also come to the region if they are interested in military history. The north of Luxembourg and nearby region of Bastogne (Belgium) saw some of the fiercest battles of World War 2 as part of the 'Battle of the Bulge'. There are a great many battlefields, museums and cemeteries relating to this, the most notable of which is the impressive American Military Cemetery of Luxembourg, which is 45 km away. The Bastogne War Museum is 27 km away, the General Patton museum 20 km and the German military cemetery 31 km. Your question is very broad, but we hope we were able to give you some interesting input. If you need any further information, don't hesitate to contact us directly. Kind regards from Luxembourg