Historical Crossword Puzzle

This is the first question for the new Fortnightly Topic Challenge #14: History.

Clues:

1. A fight near a place which was sung about 159 years later.
2. A great man dies in a city where they can't build towers.
3. A sailor discovers something other than he thought.
4. A man travels around the world in 108 minutes.
5. Trees fall over in Russia.
6. You too ...?

Instructions:

• Each clue represents a historical event.
• Each clue generates 2 entries for the crossword:
• the year of the event represented as a roman numeral
• a single word referring to the event, which can be:
• the name of a place
• the first or last name of a person
• You must find the correct position for each entry yourself.
• Allowed directions for entries are right and down.
• Only year numbers are relevant for this puzzle. AD and BC should be ignored.
• The combined colored fields will provide a clue for the final solution, a historical event that is known by each visitor of this site.
• If I had to guess without doing any actual solving of the crossword, I would think that the final solution is "birthday". – Ian MacDonald Aug 22 '16 at 18:29

The events (most of them already found by Glorfindel) are:

The battle of WATERLOO in 1815 (MDCCCXV*)
ALEXANDER the Great dies in Babylon in 323 BCE (CCCXXIII)
Christopher COLUMBUS discovers America rather than India in 1492 (MCDXCII)
Yuri Gagarin orbits the Earth with Vostok-1 in 1961 (MCMLXI)
The TUNGUSKA event felled trees in Siberia in 1908 (MCMVIII)
Julius CAESAR is murdered (And you, Brutus?), in 44 BCE (XLIV)

The resulting grid is:

. M C D X I I I X
. A W A T E R L O O
. E U I
. S M N V
. A L E X A N D E R M G
. R C C U
. C O L U M B U S
. M C V K
. C C C X X I I I A
. M V I
. L I
. X
. G A G A R I N

And the highlighted cells ...

... form another Roman numeral: DCCLXXVI or 776 BCE, the year when the first (Ancient) Olympic Games took place.

• I'm conflicted; these seems to be the right answer but @Glorfindel did most of the detective work, I do not know who to endorse. This seems to come up a lot on this site. – Avik Mohan Aug 22 '16 at 19:22
• @AvikMohan, my opinion is that this represented more than half of the work remaining, for what that's worth. But I wanted to mention for posterity "in 325 BCE (CCCXXIII)". Your Roman numeral is right, but you have 32-5, instead of 323. – John Aug 22 '16 at 19:27
• +1 - @AvikMohan I started writing the answer (and even trying to fill in the crossword - I just didn't manage to finish the upper left corner) knowing that I would not be able to finish it before attending a meeting. I'm not an experienced Puzzling SE user but I've seen this pattern (one or more answers partially solving the puzzle, and another one finishing it) before and I endorse it. – Glorfindel Aug 22 '16 at 19:40
• @DooplissForce, Aha! Or even Gaius! :) Kidding aside, that's a valid point. – John Aug 22 '16 at 20:05
• @DooplissForce That was my fault, fixed the question. – Sleafar Aug 22 '16 at 20:06

Clue 1:

Battle of Waterloo (happened in 1815 - MDCCCXV, the ABBA song is from 1974)

Clue 2 might be:

related to the Tower of Babel.

Clue 3:

Christopher Columbus discovered America in 1492 - MCDXCII, while he thought he discovered a new route to Asia.

Clue 4:

Yuri Gagarin (his Vostok 1 launched in 1961 - MCMLXI)

Clue 5 could be:

related to the Tunguska event in 1908 - MCMVIII.

Clue 6:

"You too, Brutus", which happened in 44 - XLIV BC.

• You may want to include the Roman numeral representations of the years, too. – Ian MacDonald Aug 22 '16 at 18:32
• You're right @IanMacDonald - thanks. – Glorfindel Aug 22 '16 at 18:35
• Clue 2 might be Alexander the Great who died in Babylon (323 BC). – John Aug 22 '16 at 19:07