knowledge - The hearts of gold

_{This puzzle is part 10 of Gladys' journey across the globe. Each part can be solved independently. Nevertheless, if you are new to the series, feel free to start at the beginning: Introducing Gladys.}

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Dear Puzzling,

My today's destination is an ancient landmark. This city certainly has no shortage of historic sights! No wonder they call it the █████████████

Oops, better strike out that last part. Don't want to be giving out any unintended hints, now do we?

Wish you were here!
Love, Gladys.

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_{Gladys will return in "Fieldwork ahead".}

Answer

The solution to the nonogram:

Next:

Pick up all the hearts in the maze given by the red walls...
...and the one from the blue walls.

And finally:

Use the outline of the periodic table, and take the elemental abbreviations at each heart you stop by. This gives Fl, Am, I, Ni, O(×2) from red, and Be, Li, S, K from blue: this spells out the location, the Flaminio Obelisk.