Fly to Singapore or Bali, then take a 2 hour flight to Manado,Minahasa, Northern Sulawesi. Hire a plane to fly over, or hire a car to drive up the mountain to the end of the road, then climb through rugged rainforest to peek over the edge.
I was on assignment photographing for USAID. I was to photograph the rainforest edges and illegal gold mining, but the pilot detoured to give me this view. The plane was a military plane, and I was strapped to the sides of the plane leaning out over the open 6' x 4' bombay.
Northern Sulawesi, Minahasa, sports 5 perfect volcanos, an abundance of rainforest, and crystal seas. To see this natural pit near the top of this active volcano, you have an ardous climb through rainforest, or you can see it from above.