Cultourberlin is a guide company, Madrid, Tarragona, Barcelona, Pamplona, Soria, Cadiz, etc. They do guided tours in Castilian of Berlin and its surroundings. The company was founded in 2008 and performs city walking tours, but I think you can also hire a minibus or go on cycling routes. The most popular tour is the "Essential Tour" which is ideal to discover Berlin as it visits the most important places outside the eastern part, which is where the most monuments are. Best of all, it completely breaks the visit topic of "guidance", as the explanations are pleasant, sympathetic and really interesting.