A city of two halves, Budapest is a brilliant destination for stag activities. Buda is the hilly, historic side and Pest is the party zone.
Hungary offers all sorts of awesome possibilities for stag parties with balls of steel, like caving through the city's ancient caving system and target shooting with Glocks and Magnums. There's always something new and exciting to get the old adrenaline charging.
If you want a Budapest stag do weekend with a little culture, take a city tour in clapped out Trabants and then do shots of palinka (fruit brandy) followed by cheap beers in late bars that stay open until 6am.