The crypt entrance is the tube like structure to the south of the waypoint if you can't tell as well Be careful if the dynamic event spawns, it chains like 3 or 4 (can't remember exactly) bosses that can be a pain. Otherwise run in and just dodge the oozes
As a side note if you look at the POI in your minimap, it will have a small chevron either pointing up or down to indicate the vertical difference for the location. In this case if you're above ground and looking at it on the minimap it would have a downward chevron/arrow to indicate it's underground.