town-palace is special for the personal collection of art and antiques that its owner, Regla Manjón Mergelina, who was also known as the countess of Lebrija, collected and installed in it.
She bought the place in 1901, when she was in her 50s and after her husband had already died, and started making it her personal legacy based on her interest in, and access to, art and antiquities, most of which had a connection to Andalusia.
It took her 13 years of works to re-model and refit the place so that it could host her amazing collection. She died in it in her mid-80s. The house was passed on, and lived-in, within the family and eventually in 1999, it was made into a museum.
It's absolutely worth the visit not only for its content (like the beautiful Roman mosaic in the patio that is excavated from Italica), but also to ponder about the special taste and personality of the countess!
Don't only go for the ground floor where most of the mosaics and tile work is hosted (summer residence), but make sure to include the guided visit at the second floor (winter residence). That's where her personal taste comes through more profoundly, she mixes everything with everything. This text has good hints about the place and this one has a good description.
Well, the creation of such private collection of arts and especially antiquities in not without a controversy either; wouldn't those Roman mosaics be best placed where they first belonged to? During the visit, there is hardly any material available to understand the dynamics of what went on back then (e.g. only in 1911 a law related to national partimony started stipulating such things), but this newspaper article (in Spanish) gives good insight to it (watch out for the long sentencces, though!). Here is a good posting in English. This blog post is also good, and it has very detailed pictures of the ground floor, too!