Segovia is a great city to visit for several reasons, including its historic city walls, its imposing fortress that now houses a military museum, and its huge cathedral, one of the last Gothic cathedrals to be built at a time when Renaissance architecture was already widespread. The city's main claim to fame, and the reason it stands out from the many historic towns in Castile, is its fantastic aqueduct that runs right through the city centre. A masterpiece of Roman civil engineering, and one of the best-preserved ancient monuments anywhere, it served its original purpose until the 19th century. Segovia would be an easy day trip from Madrid, but I spent the night there and could enjoy its many sights for a bit longer.