First and foremost, the Lion relief serves a structural purpose: it fills (and therefore masks) the triangular space created above the lintel in order to reduce the pressure of the tremendous weight of the stones. This “relieving triangle” aspect of the frieze can best be seen from the rear.
The forepaws of the figures rest on a row of blocks carved above a double plinth, which may represent altars. Their paws flank a single pillar, perhaps representing the propylon or entry room, symbol of the power they guard. Perhaps this was the heraldic symbol of the Royal House of Atreus. And note how the composition of the scene perfectly fits the space it is designed to occupy.
Clearly visible in the lintel and threshold of the Lion Gate are the pivot holes for double doors and holes that would have supported a wooden bar to lock the door.
An open compartment in the rock wall just inside the Lion Gate, not quite large enough to stand up straight in. Suggestions for its use range from a guard post to a gate sanctuary (or, as Paul Rehak suggests, a kennel for guard dogs!). Nobody knows for sure..