ID Tree from Youido, Seoul Korea

Hi All,

Whilst travelling to Seoul S.Korea, I saw these nice trees in the Youido area. I really would like to know what this tree is. The closest tree my searchs is the nyssa sinensis but that leave seems more narrow and isn't have the serrated. It has many leaves on a stem similar to chinese pistacio. As you can tell my knowledge is limited...

Hoping someone can identify this with their well trained eye.

 

Could be Zelkova serrata

 

Ditto to Zelkova serrata.

 

thank you soooo much...truly amazing how you can look and tell straight away. I'll take pics when i've tracked down the plant :)

 

Much planted familiar tree.