As such, a visit to the solemn and grievous site today entails a visit to the museum building, where you'll learn the site's entire history, and then walking a 2km trail (4km round-trip) across the former site, from Treblinka II - the extermination camp, to Treblinka I - the penal camp, and finally to the large victim memorial at the end - which was erected over 3 years and unveiled in 1962. The entry fee is only 7zł and goes towards upkeep of the site and the facilities here. Although not a rule, as such, it is recommended by the museum that only those 14 years of age and older enter the museum. Staff here place a high emphasis on making sure visitors understand this is a place of memorial, therefore, the usual rules apply, with no dogs allowed, no smoking etc.
Treblinka remains a backwater town, and as such travellers are going to struggle to reach it. Put simply, either hire a car and fire up the GPS for the approximately 90min drive, or contact a Warsaw-based tour companies, most of which will be happy to tailor a visit for you. Alternatively, taking a train from Warsaw Central Train Station to Małkinia is your only option. Once there, you need to take a taxi to the camp, which is less than 10km away.
With about a 3hr travel time round-trip, and 3 hrs spent on site, expect a trip to Treblinka from Warsaw to occupy the better part of a day.