Complex sentence: Ontario has 173 single-tier municipalities including 9 cities and 2 towns in southern Ontario, which are either separated from but geographically within neighbouring counties or were formed through the amalgamation of upper-tier and lower-tier municipalities.
Split into simpler sentences: Ontario has 173 single-tier municipalities including 9 cities and 2 towns in southern Ontario. Single-tier municipalities are either politically separate from but geographically within neighbouring counties or were formed through the amalgamation of upper-tier and lower-tier municipalities.