What Terezín was
Terezín was originally built in the late 18th century as a Habsburg military fortress town. During the Second World War, Nazi Germany converted it into a ghetto and transit camp — known in German as Theresienstadt — through which tens of thousands of Jewish people from Czechoslovakia and elsewhere in Europe passed, many held there for extended periods, a great many transported onward to extermination camps including Auschwitz. A separate section, the Small Fortress, operated as a Gestapo prison for political prisoners. It's one of the most significant and best-preserved Holocaust memorial sites in Central Europe.
What's there today
The Terezín Memorial (Pámátník Terezín) preserves and interprets both the ghetto town and the Small Fortress across several sites: the Ghetto Museum, exhibits within the town itself, the Small Fortress with its cells and courtyards, and a cemetery and crematorium. A single ticket typically covers the main sites, and it's possible to visit independently or with a guide — a knowledgeable guide adds real context here, more than at almost any other day trip from Prague.
Setting the right expectations
This isn't a typical day-trip stop, and it's worth planning it as its own kind of visit rather than pairing it with something upbeat. Give it real time — rushing between the Ghetto Museum, the town and the Small Fortress in an hour or two does the site a disservice. Many visitors find it emotionally heavy, appropriately so; it's worth going in with that expectation rather than treating it as another item on a sightseeing list.
It's a meaningful visit for older children and teenagers with some historical context beforehand, but most visitors would not consider it appropriate for young children.
Getting there
Direct buses run from Prague's Holoví station area, taking around an hour each way. It's straightforward to visit independently, though a guided tour can add valuable historical context if you'd prefer that over self-guided reading.