Rose Festival

Near the city is an ancient Thracian tomb dating back to 4th century BOT and is a World Heritage site. Inside the tomb is a narrow corridor opening to a round burial chamber, both of which are decorated with murals depicting a ritual funeral feast. Unfortunately, only a copy can be visited here (in the museum).
However, all other (open) tombs in the region are originals. If you are less interested in an "unoriginal" fresco, head to the Seuthes 2 & 3 and Shushmanets et al. tombs, where you can actually enter the tomb and feel a little like in Egypt.