Sejny sits in Poland's far northeast, close to Lithuania and not far from the lakes and forests of Suwalszczyzna. It is a small town, but not an ordinary one. Its best reason to stop is the feeling of a borderland: Polish, Lithuanian, Jewish, and Dominican histories all left marks within a few streets.
The clearest walk starts at the Dominican monastery and basilica, whose late Renaissance church still dominates the centre. A few minutes away, the White Synagogue has become a cultural centre run by the Borderland Foundation, turning a difficult Jewish absence into one of the town's most thoughtful spaces.
Sejny works best as a slow half day while crossing between Suwalki, Wigry, and Lithuania. If you have time, continue out to Krasnogruda Manor, the Czeslaw Milosz family estate now used for dialogue, literature, and exhibitions near the border.