I've lost my castle, how do I find where I built it?

After generating a new creative world (large biomes) I went around looking for an extreme hills biome. I did this by tping randomly in x and z directions in multiples of 10,000 (or possibly 100,000).

My problem is, I died, and hadn't reset spawn. I've opened my map in Minutor, but couldn't find it easily. How on earth do I find the castle I just built?

I found it!

MCEdit will tell you the dimensions of your world. I went to the extremities of mine, and found my castle!

I don't know whether the program you're using has this functionality, but you should filter your map for certain block types, such as glass or wood. This only spawns in a select few areas, so it will reduce the number of places you need look to find the castle again. If you have a block you only have in the castle, it will be easier to find your castle.