You can visit Bursa on a long day-trip from Istanbul. There's a lot to see in Bursa, and you'll see more if youstay overnight, but if you can't, it's still a worthwhile day-excursion.
Here are the time elements of the trip:
Your Hotel to the Ferry Dock
Istanbul—>Bursa Ferryboat Voyage
Ferry Dock to Bursa City Center
Sightseeing in Bursa
Bursa City Center to Ferry Dock
Bursa—>Istanbul Ferryboat Voyage
If you can stay at least one night in Bursa, consider visiting İznik (Nicaea) along the way to Bursa. I suggest visiting Iznik on the way to Bursa rather than on the return from Bursa to Yalova because bus transport between Bursa and Yalova is more frequent and reliable, and will help assure that you will arrive in Yalova in time to board your fast ferry to return to Istanbul.
06:45 am — Taxi or Train to Yenikapı
Take a taxi to the Yenikapı Feribot Terminali (a 10-minute ride from Sultanahmet); or a suburban train fromSirkeci or Cankurtaran stations to the Yenikapı station (a 10-minute ride), then cross the busy coastal boulevard to reach the Yenikapi Feribot Terminalı. It's a 10- to 15 minute walk between the train station and the Feribot Terminal, with traffic lights to ease the boulevard crossing.
07:30 am — Fast Ferry Istanbul (Yenikapı) to Bursa (Güzelyalı)
Buy your ticket and board the ferry at 07:15 am for a 07:30 am departure. There are usually plenty of places on the ferry for pedestrians, but if you don't want to take a chance, buy in advance or at least get to the dock early to buy your ticket. If you're shipping a car, it's best to reserve your tickets a day or so in advance if possible (although it's often possible to just drive to Yenikapi an hour in advance and buy a ticket). The voyage from Yenikapi to Güzelyali takes about 80 minutes. More...
09:00 am — Bus from Güzelyalı to the Bursaray (Metro)
Board one of the waiting yellow city buses, or a dolmush minibus, or a more expensive taxi, and ride along a four-lane road for 20 to 30 minutes to the Emek İstasyonuterminus of the Bursaray (Metro) Line M1.
9:45 am — Emek İstasyonu to Bursa City Center
Ride the Bursaray train to the Sehreküstü (sheh-REK-ew-stew) station, about 15 minutes.
10:00 am — Walk to the Ulu Cami (Great Mosque)
It's about a 10-minute walk up a gentle slope and through the bazaar to the very center of Bursa, the Ulu Cami. More...
10:10 am — Exploring Bursa
Depending on which evening ferryboat you plan to catch to return to Istanbul, you'll have five or more hours to explore Bursa's sights
Allow at least one hour to go from central Bursa via Bursaray to Emek İstasyonu and by bus or minibus to Güzelyalı. 1-1/4 or 1-1/2 hours is better.
Allow at least two hours to go from central Bursa to the bus terminal, then by bus to Yalova. 2-1/4 or even 2-1/2 hours is better.
Begin your explorations at Bursa's venerable Ulu Cami (Great Mosque). Then go next door to the Kapalı Çarşı(Covered Bazaar) being sure to stop in the Eski Aynalı Çarşı (Old Mirrored Market) for antiques and handicrafts.
Then go to the adjoining Koza Han (Silk Cocoon Caravanserai) to browse through the silks, and perhaps a refreshing glass of tea, a cool drink and/or a quick lunch in the caravanserai courtyard or in the Koza Park on the south side, by Atatürk Caddesi.
13:00 (1 pm) —
3. Minibus from İznik to Bursa
Plan to spend at least two hours in Iznik to see the major sights: the city walls, Yeşil Cami (Green Mosque), museum, etc. Then take a minibus to Bursa (67 km/34 miles, about one hour).
Minibuses wait at the dock in Yalova to whisk you off to either İznik or Bursa, as you wish. The 60-km (37-mile) ride from Yalova to İznik takes about an hour
—by Tom Brosnahan