The entrance of MUHBA, Barcelona City's History Museum, is at the 15th-century Casa Padellás, with its beautiful arcaded Gothic patio. The charts and graphs are very clear and help you recognize the historical epochs and buildings that you will come across.
FUN FACT: Casa Padellás wasn't always where you see it today: in 1931, to make way for Via Laietana, it was dismantled stone by stone and accurately moved and reassembled.