Austere
/ɒstɪə(ɹ)/
adjective
Grim or severe in manner or appearance
“The headmistress was an austere old woman.”
Lacking decoration; trivial; not extravagant or gaudy
“The interior of the church was as austere as the parishioners were dour.”
Synonyms: forbidding, stern, strict, plain, simple, unadorned, unembellished