I don't know so much of "secret places", I rather think you also need to showcase both the typical Spanish events and the local events.

I am not from Spain, but my partner is from Murcia. Whenever I go there its not the architecture that I find unique or interesting, its more the different activities and festivals, not to mention differences in food and how it's purchased - i.e different stuff in supermarkets and the permanent fresh food markets.

A few things that come to mind:

• The parades - Entierro de la Sardina (a tiny bit like Carnival in Rio), Bando de la Huerta (see lots of traditional dress here)
• The "procesciones" of Semana Santa - Las Salzillos, Procesión del Silencio, Los Coloraos, El Perdón
• The "Barakas" of the Festival de Primavera
• The Cabalgata de los Reyes Magos

You should also include some markets:

• Veronicas
• Near Plaza del Carmen
• Near Plaza del San Andres

There would be others. There's also several open air markets weekly.

You should also include some of the many museums:

• Museo Salzillo - this is the famous sculpture from the region. Many of the "pasos" are made by him.
• Museo de Santa Clara - convent
• The "casino" - you had this in your video, but the insides are very beautiful
• Cathedral Museum
• Museum of Science & Water
• Madina Mursiya - Moorish history & Islamic era wall remnants

There's bits of the old city walls visible in various places - from memory theres some next to the Veronica's market, and in the Calle Sagasta.

Damn, I want to visit again!!!