prepositions

[snade17]

Hello, Could you tell which are the right prepositions in the following sentences:
1. " Nessebar is situated on a rocky peninsula on/in the Black Sea."
2. " Boyana Church is located on/in the outscirts of Sofia."
3. " Many writers, singers, actors, artists flock to Sofia in/at the start of June.

[Tdol]

on
on
at