This entry is about (the legendary conference Como 1990 and) the excellent proceedings volume
which is one of the overall historical heights of the (quality content of the) proceedings within the tradition of conferences in pure category theory. Now it is even hard to find a publisher for contemporary category conference proceedings…
The preface is
Some of the articles include the following.
A. Joyal, M. Tierney, Strong stacks and classifying spaces, 213–236 (pdf)
(on (2,1)-sheaves and 2-sheaves).
S. Kasangian, S. Vigna, Trees in distributive categories, 237–248
A. Kock, Algebras for the partial map classifier monad, 262–278
F. W. Lawvere, Intrinsic co-Heyting boundaries and the Leibniz rule in certain toposes, 279–281
(see also at co-Heyting algebra)
Duško Pavlović, Categorical interpolation: descent and the Beck-Chevalley condition without direct images, 306–325 ($n$lab remark: important clarification of the subject from logics point of view).
A. J. Power, An $n$-categorical pasting theorem, 326–58
(on pasting in n-categories).
G. E. Reyes, H. Zolfaghari, Topos-theoretic approaches to modality, 359–378
(on modal logic in topos theory).
S. H. Schanuel, Negative sets have Euler characteristic and dimension, 379–385
M. Thiébaud, Modular categories, 386–400
J. J. C. Vermeulen, Some constructive results related to compactness and the (strong) Hausdorff property for locales, 401–409
(on locales).
A. Joyal, R. Street, An introduction to Tannaka duality and quantum groups, 413–492
…
About the geographic place see wikipedia: Como and the conference centre : Villa Olmo.