Altitude

To begin with, I went to Wikipedia and made inquiries about what altitude above sea level is and from which sea it should be calculated. Here's what they write there:
Height above sea level is a coordinate in three-dimensional space (the other two are latitude and longitude), showing at what level relative to sea level taken as zero this or that object is located.
The Baltic altitude system (BSV) is a system of absolute altitudes adopted in the USSR in 1977, which is counted from the ground zero in Kronstadt. The heights of reference geodetic points are measured from this mark, which are marked on the ground with various geodetic signs and plotted on maps. Ukraine inherited this system, so the elevations on Ukrainian topographic maps are given in BSV.

In theory, everything is clear - you need to take a detailed topographic map and see what heights are indicated there. But where do you get such a map?
The first thing that came to mind was to look into OziExplorer. This is a special program for working with GPS (satellite navigator). One of its functions allows you to determine the height simply by pointing the cursor at a place on the map. With her help, I easily found out that Alushta is located at altitudes from 0 to 130 meters above sea level. Yalta - from 0 to 200 meters, Sevastopol - from 0 to 100, Simferopol - on average 250 meters above sea level.

However, this method is not very universal. After all, the question still remains: “where can I get a map?”, this time digitized. I had maps of Crimea, but things didn’t work out with the rest of the world...

The answer literally lay on the surface, that is, on the Internet. For several years now, the service Google Earth has been operating there - a kind of digital globe glued together from photographs of the earth’s surface from a “cosmic” height. There certainly should be a height detection function. I downloaded the Google Earth distribution (free version), installed it and started exploring the menu. There were no altimeters there. Strange... Maybe I should read the certificate? I didn't find it either:(
Almost in despair, I suddenly noticed numbers running quickly at the bottom of the screen. Eureka!!! This was the altimeter.

To celebrate, I began to run around the map and measure the height of all the cities in a row.

The height of Yekaterinburg above sea level is 250 meters.
The height of Moscow above sea level is 130 meters.
Saratov - 40
Makhachkala - 15
Krasnoyarsk - 140
Perm - 150
Chelyabinsk - 250
Ufa - 125
Kazan - 90
Nizhny Novgorod - 70
Ivanovo - 130
Yaroslavl - 98
Voronezh - 104
St. Petersburg - 13
Arkhangelsk - 7
Novgorod - 28
Murom - 105

Altitude above sea level of some cities in Ukraine:
The height of Kyiv above sea level is from 90 (the level of the Dnieper) to 190 (the famous Dnieper steeps) meters.
Kharkiv - 122
Chernivtsi - 240
Khmelnytskyi - 299
Ternopil - 336
Vinnytsia - 294
Cherkasy - 80
Kryvyi Rih - 85
Zaporizhzhia - 75
Kherson - 50
Donetsk - 241
Dnipro - 68
Sumy - 125
Poltava - 150
Chernihiv - 117

In the western part of Ukraine I was interested in the heights of such settlements:
Lviv - 270
Ivano-Frankivsk - 343
Uzhhorod - 187
Mukachevo - 181
Rakhiv - 430
Yasinia - 650
Yablunytskyi Pass - 930

I hope you understand that all the data obtained is not very accurate. Google Earth is not a professional tool with guaranteed accuracy and reliably known errors. She has completely different goals.
In addition, the term “city height above sea level” itself is very conditional. After all, a city is not a point, but a huge object, different areas of which have different heights.