سَافَرْتُ إِلَى بَعْلَبَكَّ — I travelled to Baalbek.
سَافَرْتُ: past verb plus subject pronoun.
إِلَى: preposition.
بَعْلَ: fixed first part.
بَكَّ: genitive with fatḥah under the diptote rule.
The same principle holds after other suitable prepositions, not only بِـ: the final component is genitive but takes fatḥah in place of kasrah.