I cannot think of a "slang" word for "curiosity".  However, if you decide to use a standard word, you could label the section of your blog "Curiosities".   There is nothing "unfriendly" about that word.

(As you probably know, the word “curiosity” means not only a desire to learn or know something; it also means an object or thing that arouses your interest in learning about it, because it is different or extraordinary.  So when you are talking about more than one such thing in Barcelona, you should use the plural “curiosities.”)

If the things you are going to write about are truly marvelous (wonderful), you could call label the section of your blog “Marvels”.  The word “marvels” sounds very attractive.

hi,

its difficult to turn curiosity into slang. normally the term 'nosiness' is used to express hypercuriosity or to a degree which is  bothering. 'snoopiness' is another one but please remember both of these terms are very informal and the person indicated may take offense. 

interest/concern/regard are rather friendlier options.