Hotel Ametyst sits in Vinohrady — one of Prague's best neighbourhoods for a stag do. You're a 15-minute walk from Wenceslas Square, but far enough from the tourist crowds to actually sleep at night. The hotel is 4-star, which means proper beds, air-conditioned rooms, free Wi-Fi, mini-bar, and a breakfast buffet to sort the group out before a big day.
It's a solid base. Not flashy, but clean, well-run, and the kind of place that doesn't flinch when 12 lads check in for the weekend.