Hello, I am Yoshi from NILS Japanese language school.
[N1 (place)に　N2が　あります／います]
1) The place where N2 is present is indicated by the particle に.
(Example)
わたしの　部屋（へや）に　机（つくえ）が　あります。　　　There is a desk in my room.
事務所（じむしょ）に　スミスさんが　います。　　　Mr. Smith is in the office.
*部屋：　room
*机：　desk
*事務所：　office

2) You can ask what or who is present at/in the place by using this pattern. The interrogative なに is used for things and だれ is used for persons.
(Example)
地下に　何（なに）が　ありますか。　　　—レストランが　あります。
What is there in the basement?　　　—There are restaurants.
受付に　だれが　いますか。　　　—田中さんが　います。
Who is at the reception desk?　　　—Ms. Tanaka is there.
*地下：　basement
*受付：　reception desk

August 1st News, from NILS Japanese language school.