I usually end up with an unassuming hole in the ground and sometimes a small tower to defend it. A tunnel goes around a curve or down ramps to the reception area, a large chamber that usually has the trade depot & staging for aboveground work. From there, ramps or stairs lead down through an inner gate, and rough stone gives way to the polished floors & wide halls of the opulent fortress proper. I like the thought of a traveler entering a muddy hole and following a rough stone tunnel which suddenly opens into a cavernous meeting hall covered with masterful engravings and packed with life.
I do sometimes build extensive aboveground works. Sometimes these fall into the category of traditional castle / walled city architecture, with a curtain wall around a central building (which is sometimes just my usual hole + tower). Gatehouses in the outer wall use a drawbridge over a moat or an elevated drawbridge to a freestanding external structure.
At this site, visitors cross the dry moat on a drawbridge under fortifications flush with the curtain wall. They pass through a short dark hall before emerging into an open courtyard surrounded by arrow-slits on all sides. Leaving the gatehouse, they cross the broad courtyard before going under the white structure at the top of the picture which shades the entrance to the fortress.
The biggest deviation from my usual habits has to be Babinusan, "Friendlymurders". There are no outbuildings, no curtain wall, no courtyards, just a single huge marble & obsidian building that sprawls atop a bluff in the swamps. The structure towers over visitors as they come up the hill towards the main gate, concealed by a bend in the wall. Going around the corner, our guests cross a drawbridge and descend a ramp. At the bottom of the ramp, several stories underground, are more drawbridges that control whether they get a direct route in or cross a dodge-me trap over magma
Beyond the main drawbridge, the hall curves several times as it passes the primary military killing zone. It then curves 180 degrees down more ramps to the trade depot. One level below the trade depot, it finally opens out into an industrial area of the fortress proper.
Beyond the dodge-me trap are cave crocodiles.
Note the lava dispenser covering the approach to the gate and the black tower containing the magma pump stack.