。
This time tomorrow I'll be touring Paris.
Literal
Tomorrow [possessive-の] this-about-time [topic-は] Paris [possessive-の] inside-city tour [object-を] be-doing probably.
市内 literally 'city-inside' — a Sino-Japanese compound contrasting with 市外 ('outside the city'). 市内観光 ('tour inside the city') is a set collocation used in tourist guides. 今ごろ + ~ているでしょう projects an ongoing future activity onto a specific time.