A layover is time you have already paid for. Extend it deliberately and the trip gains a city, sometimes without adding anything to the fare.
Layover, stopover, and why the words matter
A layover is a short connection, a few hours between flights. A stopover is a longer deliberate pause, typically overnight or several days, in a connecting city before you fly on. Booking engines treat them differently, and so do airlines: the second one is often a product with its own name and rules.
Airlines that encourage it
Hub carriers like stopovers because they fill their home-base flights and hand their country extra tourism. Icelandair has run its Reykjavík stopover for decades, TAP offers one in Lisbon or Porto, Turkish Airlines has an Istanbul stopover that includes a hotel on qualifying itineraries, Emirates sells Dubai Connect, Qatar has a Doha programme, and Finnair, Copa and Singapore Airlines have all run versions of the same idea.
Terms change often, so check the airline's own stopover page for the itinerary you are looking at rather than trusting a list, including this one. The pattern to look for is straightforward: if your route already connects through a carrier's hub, extending the stop is frequently free or close to it.
Building one yourself
Start from the connection city, not the fare. A cheap itinerary through somewhere you have no interest in is just a long day.
Then give yourself real time. A stopover needs enough hours to clear immigration, get into the city, sleep, and come back with a buffer. Check the entry rules for the connecting country before you commit, because a transit that never leaves the airport and a stopover that does are two different visa questions.
Prefer a single ticket. If you build the trip from separate bookings, the airlines owe you nothing when the first leg is late, so leave a generous cushion and expect to re-check bags.
Travel light for it
A stopover is much easier with a cabin bag only: nothing to collect, nothing to re-check, and you can be on a train into the city while the rest of the flight is still at the carousel.
Finding the routes worth stopping in
The combination you want is a connecting fare that is both cheap and routed through somewhere you would like to see. Setting alerts on a few such routes at once is a reasonable way to let that combination find you: when one of them drops to your price, the layover is already in the itinerary. Browse destinations and pick two or three worth watching.
