Sebastopol is a proper noun, most commonly referring to a port city in Crimea or California, or to the historical Russian stronghold of Sebastopol. The word functions as a place name and is typically stressed on the second syllable in common usage, often pronounced with a three-syllable rhythm in English. In practice, you’ll hear it pronounced with a soft “t” or omitted in rapid speech, depending on speaker and context.
Full pronunciation guide