A four-hour domestic layover and a four-hour international arrival can behave like completely different trips. The difference is not just distance. It is paperwork, customs, terminal changes, and the chance that your bag must be reclaimed.
Domestic is usually simpler
If both flights are domestic and on one ticket, you often stay airside and skip security entirely. Leaving the airport adds a new security line, so the city trip needs to be worth that extra risk.
International arrivals need more buffer
International arrivals may require immigration, baggage claim, customs, bag recheck, and another security screening before the next flight. That can erase the useful part of a layover quickly.
Same ticket matters
Separate tickets are less forgiving. You may need to collect bags, check in again, and meet the second airline's cutoff time. Treat separate-ticket layovers like a mini departure day.