Casa Batllo was built in 1904-1906 as a residence for the Batllo family. Today it is a museum. The house is located on Passeig de Gracia north of Placa de Catalunya, and is easily accessible from the hop-on, hop-off bus or by taxi. The exterior is covered with mosaics, glass, and ironwork. One thing you will not see in the interior is a straight wall or line. It is filled with curved walls, doors, colorful windows, and stairways. The roof is topped with artwork similar to that seen on other Gaudi designs.
The entry fee (13.5 euros with Turista bus discount) is steep, but the tour (with earphones in different languages) is fascinating and worth the cost.