There is a small building upon the platform of the Oathgate in the city, which had once included only a section near the center called the Ancient Ward. This raised portion had a distinctive shape formed by the way the rocks had been carved millennia ago.
The city has long since been built beyond that. A lower section called the Low Ward clutters stones around the base of a wall - a wide, squat fortification to the west that runs from cliffs on one side of the city to to the mountain foothills on the other.
Above and behind the Ancient Ward, the city expands up a series of steplike tiers. These Loft Wards end at a majestic Royal Ward at the top of the city, holding palaces, mansions, and temples. The Oathgate platform is on this level, at the northern edge of the city, close to the cliffs down to the ocean.
According to Dalinar, this place once would've been stunning because of its magnificent architecture. Presently, dozens ... hundreds of buildings have fallen in. Entire sections have become rubble when higher structures, smashed by the Everstorm, have slid down on top of them. What had once been one of the finest cities of all Roshar - known for its art, trade, and fine marble - is cracked and broken.
Ironically, more modest buildings at the base of the city - in the wall's shadow - have weathered the storm. But the famous Thaylen docks are out beyond this fortification, on the small western peninsula fronting the city. This is an area that had once been densely developed ... likely with warehouses, taverns, and shops. All made of wood.
Dalinar observes that they've all been swept away completely. Only smashed ruins remain.
Most of this destruction was caused by the first full Everstorm; Thaylen City was particularly exposed, with no land to break the storm as it surged across the western ocean. Beyond that, many more of the city's structures had been of wood, particularly in the Loft Wards. According to Dalinar's thinking, a luxury to a place like Thaylen City, which until today had been subject to only the most mild of storm winds.