Hattuşa's star attraction is this postern gate complex with an artificial mound pierced by a 70m-long tunnel. The Hittites built the tunnel using a corbelled arch (two flat faces of stones leaning towards one another), as the 'true' arch was not invented until later.
Primitive or not, the arch of Yer Kapı has done its job for millennia, and you can still pass down the stony tunnel as Hittite soldiers did, emerging from the postern. Afterwards, re-enter the city via one of the monumental stairways up the wide stone glacis and pass through the Sphinx Gate, once defended by four great sphinxes. Of the original statues, one is still in situ, two are in the Boğazkale Museum and the other has been lost. The two replica sphinxes gracing the inner gate here used to call the Boğazkale Museum home before the originals were returned in 2011.
There are wonderful views over the upper city temple district from here.