Surabaya is a good base for exploring East Java. All destinations below are reachable by bus from Bungurasih terminal or by train from Gubeng Station.
Madura is the closest excursion -- a ferry ride across the strait from Tanjungperak. The Jalesveva Jayamahe Monument at the naval base is visible from the boat. Malang is a pleasant retreat from Surabaya's heat, with colonial-era architecture, Hindu temples, and the hill resort of Selecta. Sidoarjo is the place for East Javanese street food and cheap leather goods. Pasuruan and Probolinggo are the entry points for Bromo-Tengger-Semeru National Park and the spectacular Madakaripura waterfall.