I converted to Judaism, becoming friendly with Hammy, as we divided our continent. I built the Colossus while bee-lining for optics. My caravels met Genghis and Gilgamesh, who were friendly with each other, after having divided Egypt between them before I ever made contact. Having circumnavigated, my caravels came home, while I avoided Astronomy as long as I could, to keep the bonus from the Colossus going.
I built up my science and technology, but I ultimately decided that Hammy would be my rival for any peaceful victory, while launching a long-distance invasion from only my half of my continent seemed unwise. So...Hammy had to go. I declared war (very late for a Civ game) in 1765 and eliminated the Babylonian Empire in 1858.
I began building up an invasion fleet. Genghis had switched religions, so he wasn't on such good terms with Gilgamesh any more. When I noticed he was at WHEOORN, I assumed he'd be attacking his neighbor and I could come to Sumeria's "rescue". So it was quite a surprise when Genghis declared war on me in 1880, launching a surprise amphibious assault against the city where my own army and fleet were massing. Unfortunately for him, a fleet of caravels and galleons couldn't bombard, his inferior land units died on the beaches, and his fleet never sailed home again.
But wait! That invasion turned out to be a feint, as I noticed an even larger fleet was heading toward my southern coast! I rushed units to reinforce my cities on that coast, as my frigates (and soon, destroyers) picked off the many caravels guarding his galleons. His fleet pushed further and further along my southern coast as it was relentlessly chased and whittled down, with his survivors finally landing on a patch of tundra in 1898 and being wiped out there.
My own invasion force landed in 1903 and I eliminated Genghis by 1934. War with Gilgamesh immediately followed, and I crossed the Domination victory threshold in 1944. A long and slow game that will surely end up in the middle of the rankings (as usual). Not being able to vassalize one's enemies certain does drag things out.