IAN: Oh, it's enormous!

BARBARA: Look at the joins in the blocks, Ian.

IAN: Yes, no mortar. Must have been built with tremendous accuracy.

BARBARA: Yes, the Egyptians did the same thing. So did the Indians of Central and Southern America.

IAN: A precise distribution of weight, that's the key, isn't it?

BARBARA: Yes. Marvelous, isn't it?

DOCTOR: Yes, now before you two get carried away, I think we'd better go and find Susan, hmm?

BARBARA: Yes, you're quite right.