Both Uses of

pavilion
in
The Magic Mountain

From boyhood on, these were all familiar sights to Hans Castorp, awakening in him a warm sense of belonging, a feeling that reached its zenith, perhaps, on those occasions when he would join James Tienappel or his cousin Ziemssen— Joachim Ziemssen—in the pavilion on the Alster for a Sunday breakfast of warm rolls and smoked beef, washed down by a glass of old port, then lean back in his chair and puff devotedly on his cigar.†
Chpt 2.2

pavilion = a large structure separate from a main structure or temporary

There was music in the air, the hotel band was playing a concert from a little gallery on the wooden pavilion at the far end of the rectangular rink, behind which snowcapped mountains rose against a deep blue sky.†
Chpt 5.8 *

Definitions:

(1) (pavilion)
a large structure separate from a main structure
in various senses, including:
- a large roofed structure without walls -- often found in parks
- a temporary structure -- such as a large tent to house exhibits at a fair, to provide sports facilities, or to put on a show
- a section of a large hospital or office complex adjacent to other parts
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

Much more rarely, pavilion can reference a facet of a gem or part of the outer ear.