Barcelona - best authentic/most unforgettable local travel experiences.

I am slowly traveling around Europe. Barcelona is my first destination. I have all the time in the world to explore its many secrets.  What are the not-to miss ideas, places, and specialties, that are OFF the beaten path but worth a peak. Please share your favourite suggestions, as I have below, according to the following interest criteria. Thank you in advance.

-memorable/dramatic scenery & landscape photography. Where do I find the best (viewpoints, city views, panoramas, skylines, sunsets, etc..)?
-the unique outdoors, hikes/hilltops/lookouts, and amazing views…
-lovely/charming streets, magnificent/attractive (off-the beaten path) architecture
-non-typical, interesting/special experiences (full of original character), and unique only to the local area.
-specialty/unique local cuisine, the best freebies/and anything else off-the beaten path worth mentioning.

Thanks again…

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BARCELONA

Parc de Collserola (city view)
Parc Guell (take a picnic)
Parc de la Cuitadella
Parc d’en Castell de l’Oreneta (cityview)

At sunset,
walk along Passeig Maritim, cross the Vila Olimpica, continue to la Barceloneta, follow el moll de la Fusta to Colon monument at sunset.
Palau Nacional (MNaC) at Montjuic castle
tibidabo city view
Top of Villa Olympica

horchata, cava
chocolate con churros

La plata, fried sardines and wine, The combination sounds delicious…
Origen 99.9% - The next four items are cheap eats, but who knows if they’re authentic?
Txappela,
Tapa Tapa
La Fona, puerto olympico
EAT at World trade center for cheap eats? Is it true?
Comer y no Bombas (free vegen food) I dont know if it’s really free, but who knows.  Where can I get it?
TRAVEL BAR - C/ Boqueria 27, Directions: They offer 1 euro lunch? Has anyone tried it?

Sardana - traditional Catalan dance in Cathedral Square on Sundays from 12-2, Place de la Seu
Montserrat, monastery at 1pm choir - is this religious site worth the trip?